IMT Institutional Repository: No conditions. Results ordered -Date Deposited. 2024-03-29T09:01:38ZEPrintshttp://eprints.imtlucca.it/images/logowhite.pnghttp://eprints.imtlucca.it/2022-01-26T08:15:05Z2022-02-09T08:33:39Zhttp://eprints.imtlucca.it/id/eprint/4083This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40832022-01-26T08:15:05ZThe Effect of Short-Term Rentals on Local Consumption Amenities: Evidence from MadridThis paper investigates the impact of the arrival of Airbnb on the local consumption amenities in Madrid. We exploit the exogenous variation created by the timing and the unequal distribution of Airbnb listings across the urban geography to identify its effects on food and beverage establishments. Using an instrumental variable strategy, we find positive local effects on both the number of restaurants and their employees: an increase in ten Airbnb rooms in a given census tract translates into one more restaurant, and the same increase in a given neighborhood generates nine new tourist-related employees. The results are robust to sample composition, spatial spillovers and alternative measures of local consumption amenities. This paper contributes to the literature on the economic impacts of the platform economy on urban areas by providing evidence of positive economic externalities from short-term rentals.Alberto Hidalgoalberto.hidalgo@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itFrancisco J. Velázquez2021-03-17T10:04:23Z2021-03-17T10:04:50Zhttp://eprints.imtlucca.it/id/eprint/4081This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40812021-03-17T10:04:23ZA Neural Network Ensemble Approach for GDP
ForecastingWe propose an ensemble learning methodology to forecast the future US GDP
growth release. Our approach combines a Recurrent Neural Network (RNN) with
a Dynamic Factor model accounting for time-variation in mean with a General-
ized Autoregressive Score (DFM-GAS). The analysis is based on a set of predictors
encompassing a wide range of variables measured at different frequencies. The
forecast exercise is aimed at evaluating the predictive ability of each model's com-
ponent of the ensemble by considering variations in mean, potentially caused by
recessions affecting the economy. Thus, we show how the combination of RNN and
DFM-GAS improves forecasts of the US GDP growth rate in the aftermath of the
2008-09 global financial crisis. We find that a neural network ensemble markedly
reduces the root mean squared error for the short-term forecast horizon.Luigi Longoluigi.longo@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itArmando Rungiarmando.rungi@imtlucca.it2020-10-05T08:12:33Z2020-10-05T08:12:33Zhttp://eprints.imtlucca.it/id/eprint/4079This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40792020-10-05T08:12:33ZImproving the Prediction of Clinical Success Using Machine LearningIn pharmaceutical research, assessing drug candidates’ odds of success as they move through clinical
research often relies on crude methods based on historical data. However, the rapid progress of
machine learning offers a new tool to identify the more promising projects. To evaluate its usefulness,
we trained and validated several machine learning algorithms on a large database of projects. Using
various project descriptors as input data we were able to predict the clinical success and failure rates
of projects with an average balanced accuracy of 83% to 89%, which compares favorably with the 56%
to 70% balanced accuracy of the method based on historical data. We also identified the variables that
contributed most to trial success and used the algorithm to predict the success (or failure) of assets
currently in the industry pipeline. We conclude by discussing how pharmaceutical companies can use
such model to improve the quantity and quality of their new drugs, and how the broad adoption of
this technology could reduce the industry’s risk profile with important consequences for industry
structure, R&D investment, and the cost of innovation.Bernard Munosbernard.munos@gmail.comJan Niederreiterjan.niederreiter@alumni.imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2020-06-15T11:52:24Z2020-06-15T12:06:00Zhttp://eprints.imtlucca.it/id/eprint/4077This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40772020-06-15T11:52:24ZMachine Learning for Zombie Hunting.
Firms’ Failures and Financial Constraints.In this contribution, we exploit machine learning techniques to predict the risk of failure of firms.
Then, we propose an empirical definition of zombies as firms that persist in a status of high
risk, beyond the highest decile, after which we observe that the chances to transit to lower risk
are minimal. We implement a Bayesian Additive Regression Tree with Missing Incorporated in
Attributes (BART-MIA), which is specifically useful in our setting as we provide evidence that
patterns of undisclosed accounts correlate with firms’ failures. After training our algorithm
on 304,906 firms active in Italy in the period 2008-2017, we show how it outperforms proxy
models like the Z-scores and the Distance-to-Default, traditional econometric methods, and
other widely used machine learning techniques. We document that zombies are on average
21% less productive, 76% smaller, and they increased in times of financial crisis. In general,
we argue that our application helps in the design of evidence-based policies in the presence of
market failures, for example optimal bankruptcy laws. We believe our framework can help to
inform the design of support programs for highly distressed firms after the recent pandemic
crisis.Falco J. Bargagli-Stoffifalco.bargaglistoffi@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itArmando Rungiarmando.rungi@imtlucca.it2019-12-16T16:23:45Z2019-12-16T16:23:45Zhttp://eprints.imtlucca.it/id/eprint/4073This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40732019-12-16T16:23:45ZTalents from Abroad. Foreign Managers and Productivity in the United Kingdom.In this paper, we test the contribution of foreign management on firms’ competitiveness. We use a novel dataset on the careers of 165,084 managers employed by 13,106 companies in the United Kingdom in the period 2009-2017. We find that a domestic manufacturing firm becomes on average between 9% and 12% more productive after hiring at least one foreign manager. Interestingly, productivity gains by domestic firms after recruiting foreign managers are similar in magnitude to gains after foreign acquisitions as from previous literature. Eventually,
we do not find significant gains by foreign-owned firms hiring foreign managers.
Our identification strategy combines difference-in-difference and matching techniques to challenge reverse causality. We proxy firms’ competitiveness either by total factor productivity or by technical efficiency derived from stochastic frontier analyses. Eventually, we argue that limits to the circulation of talents, as for example in case of a Brexit event, may hamper the allocation of labor productive resources.Dimitrios Exadactylosdimitrios.exadactylos@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itArmando Rungiarmando.rungi@imtlucca.it2018-10-04T08:13:03Z2018-10-05T07:33:27Zhttp://eprints.imtlucca.it/id/eprint/4072This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40722018-10-04T08:13:03ZBrain-Circulation Network: The Global Mobility of the Life ScientistsGlobal mobility and migration of scientists is an important modern phenomenon with economic and
political implications. As scientists become ever more footloose it is important to identify general patterns
and regularities at a global scale. At the same time cities, and especially global cities, have become impor-
tant loci of economic and scientific activity. Limiting research to international migration, would disregard
the importance of local innovation systems. The analysis of the mobility and brain circulation patterns at
global scale remains challenging, due to difficulties in obtaining individual level mobility data. In this work
we propose a methodology to trace intercity and international mobility through bibliographic records. We
reconstruct the intercity and international mobility network of 3.7 Million Life Scientists moving between
9,745 cities. We present several features of the extracted network, offer evidence that the international
innovation system is marked by national borders and linguistic similarity and show that international mo-
bility largely contributes to the scientific output of national research systems. Moreover we find evidence to
suggest that global cities attract highly productive scientist early in their careers.Luca Verginerluca.verginer@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2018-01-16T10:04:27Z2018-01-16T10:04:27Zhttp://eprints.imtlucca.it/id/eprint/3861This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38612018-01-16T10:04:27ZThe Network of U.S. Mutual Fund Investments: Diversification, Similarity and Fragility throughout the
Global Financial CrisisNetwork theory proved recently to be useful in the quantification of many properties of financial systems. The analysis of the structure of investment portfolios is a major application since their eventual correlation and overlap impact the actual risk diversification by individual investors. We
nvestigate the bipartite network of US mutual fund portfolios and their assets. We follow its evolution during the Global Financial Crisis and analyse the interplay between diversification, as understood in classical portfolio theory, and similarity of the investments of different funds. We show that, on average, portfolios have become more diversified and less similar during the crisis. However, we also find that large overlap is far more likely than expected from models of random allocation of investments. This indicates the existence of strong correlations between fund portfolio strategies. We introduce a simplified model of propagation of financial shocks, that we exploit to show that a systemic risk component origins from the similarity of portfolios. The network is still vulnerable after crisis because of this effect, despite the increase in the diversification of portfolios. Our results indicate that diversification may even increase systemic risk when funds diversify in the same way. Diversification and similarity can play antagonistic roles and the trade-off between the two should be taken into account to properly assess systemic risk.Danilo DelpiniStefano BattistonGuido Caldarelliguido.caldarelli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2018-01-12T08:24:38Z2018-01-12T08:24:38Zhttp://eprints.imtlucca.it/id/eprint/3856This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38562018-01-12T08:24:38ZThe Global Health Networks:
A Comparative Analysis of
Tuberculosis, Malaria and Pneumonia
Using Social Media DataGlobal health networks (GHNs) of organizations fighting major health threats
represent a useful strategy to respond to the challenge of mobilizing and coordinating
different types of health organizations across borders toward a common goal.
In this paper we reconstruct the GHNs of malaria, tuberculosis and pneumonia by
creating a new unique database of health organizations from the official Twitter accounts
of each organization. We use a majority voter Multi Naive Bayes classifier to
discover, among the Twitter users, the ones that represent organizations or groups active
in each disease area. We perform a social network analysis (SNA) of the global
health networks (GHNs) to evaluate the structure of the network and the role and
performance of the organizations in each network. We find evidence that the GHN
of malaria, TBC and pneumonia are different in terms of performance and leadership,
geographical coverage as well as Twitter popularity. Our analysis validate the
use of social media to analyze GHNs, their effectiveness and to mobilize the global
community toward global sustainable development.Milena LopreiteMichelangelo Puligamichelangelo.puliga@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2017-12-28T11:09:29Z2017-12-28T11:09:29Zhttp://eprints.imtlucca.it/id/eprint/3853This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38532017-12-28T11:09:29ZWhere Gibrat meets Zipf: scale and scope of French firmsThe proper characterization of the size distribution and growth of firms represents an important issue in economics and business. We use the Maximum Entropy approach to assess the plausibility of the assumption that firm size follows Lognormal or Pareto distributions, which underlies most recent works on the subject. A comprehensive dataset covering the universe of French firms allows us to draw two major conclusions. First, the Pareto hypothesis for the whole distribution should be rejected. Second, by discriminating across firms based on the number of products sold and markets served, we find that, within the class of multi-product companies active in multiple markets, the distribution converges to a Zipf’s law. Conversely, Lognormal distribution is a good benchmark for small single-product firms. The size distribution of firms largely depends on firms’ diversification patterns.Marco BeeMassimo Riccabonimassimo.riccaboni@imtlucca.itStefano Schiavo2017-12-28T11:06:06Z2017-12-28T11:06:06Zhttp://eprints.imtlucca.it/id/eprint/3852This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38522017-12-28T11:06:06ZThe indirect effects of foreign direct investment on trade: A network perspectiveThe relationship between international trade and foreign direct investment (FDI) is one of the main features of globalisation. In this paper, we investigate the effects of FDI on trade from a network perspective, since FDI takes not only direct but also indirect channels from origin to destination countries because of firms’ incentive to reduce tax burden, to minimise coordination costs and to break barriers to market entry. We use a unique data set of international corporate control as a measure of stock FDI to construct a corporate control network (CCN), where the nodes are the countries and the edges are the corporate control relationships. Network measures, as the shortest path length and the communicability, are then computed on the CCN to capture the indirect channel of FDI. Empirically, we find that corporate control has a positive effect on trade both directly and indirectly. The result is robust with different specifications and estimation strategies. Hence, our paper provides strong empirical evidence of the indirect effects of FDI on trade. Moreover, we identify a number of interplaying factors such as regional trade agreements and the region of Asia. We also find that the indirect effects are more pronounced for the manufacturing sector than for primary sectors such as oil extraction and agriculture.Rodolfo MetuliniMassimo Riccabonimassimo.riccaboni@imtlucca.itPaolo SgrignoliZhen Zhu2017-12-28T11:03:30Z2017-12-28T11:03:30Zhttp://eprints.imtlucca.it/id/eprint/3851This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38512017-12-28T11:03:30ZConsistency and Trends of Technological Innovations: A Network Approach to the International Patent Classification DataClassifying patents by the technology areas they pertain is important to enable information search and facilitate policy analysis and socio-economic studies. Based on the OECD Triadic Patent Family database, this study constructs a cohort network based on the grouping of IPC subclasses in the same patent families, and a citation network based on citations between subclasses of patent families citing each other. This paper presents a systematic analysis approach which obtains naturally formed network clusters identified using a Lumped Markov Chain method, extracts community keys traceable over time, and investigates two important community characteristics: consistency and changing trends. The results are verified against several other methods, including a recent research measuring patent text similarity. The proposed method contributes to the literature a network-based approach to study the endogenous community properties of an exogenously devised classification system. The application of this method may improve accuracy and efficiency of the IPC search platform and help detect the emergence of new technologies.Yuan GaoZhen ZhuMassimo Riccabonimassimo.riccaboni@imtlucca.it2017-11-13T15:58:37Z2017-11-13T15:58:37Zhttp://eprints.imtlucca.it/id/eprint/3827This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38272017-11-13T15:58:37ZOn Economic Complexity and the Fitness of NationsComplex economic systems can often be described by a network, with nodes representing economic entities and edges their interdependencies, while network centrality is often a good indicator of importance. Recent publications have implemented a nonlinear iterative Fitness-Complexity (FC) algorithm to measure centrality in a bipartite trade network, which aims to represent the ‘Fitness’ of national economies as well as the ‘Complexity’ of the products being traded. In this paper, we discuss this methodological approach and conclude that further work is needed to identify stable and reliable measures of fitness and complexity. We provide theoretical and numerical evidence for the intrinsic instability in the nonlinear definition of the FC algorithm. We perform an in-depth evaluation of the algorithm’s rankings in two real world networks at the country level: the global trade network, and the patent network in different technological domains. In both networks, we find evidence of the instabilities predicted theoretically, and show that ‘complex’ products or patents tend often to be those that countries rarely produce, rather than those that are intrinsically more difficult to produce.Greg MorrisonSergey V. BuldyrevMichele ImbrunoOmar Alonso Doria ArrietaArmando Rungiarmando.rungi@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itFabio Pammolli2017-07-17T09:56:03Z2017-07-18T09:29:07Zhttp://eprints.imtlucca.it/id/eprint/3721This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37212017-07-17T09:56:03ZFestivals, institutional maintenance and change: The case of the Lucca Comics & Games FestivalYesim Tonga Uriarteyesim.tonga@imtlucca.itRobert J. DeFilippiMassimo Riccabonimassimo.riccaboni@imtlucca.itMaria Luisa Catonimarialuisa.catoni@imtlucca.it2017-05-08T12:56:40Z2018-01-31T12:42:32Zhttp://eprints.imtlucca.it/id/eprint/3700This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37002017-05-08T12:56:40ZModeling networks with a growing feature-structureWe present a new network model accounting for multidimensional assortativity. Each node is characterized by a number of features and the probability of a link between two nodes depends on common features. We do not fix a priori the total number of possible features. The bipartite network of the nodes and the features evolves according to a stochastic dynamics that depends on
three parameters that respectively regulate the preferential attachment in the transmission of the features to the nodes, the number of new features per node, and the power-law behavior of the total number of observed features.
Our model also takes into account a mechanism of triadic closure. We provide theoretical results and statistical estimators for the parameters of the model.
We validate our approach by means of simulations and an empirical analysis of a network of scientific collaborations.Irene Crimaldiirene.crimaldi@imtlucca.itMichela Del Vicariomichela.delvicario@imtlucca.itGreg Morrisongreg.morrison@imtlucca.itWalter Quattrociocchiwalter.quattrociocchi@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2017-04-03T09:39:32Z2017-08-28T15:31:01Zhttp://eprints.imtlucca.it/id/eprint/3683This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36832017-04-03T09:39:32ZAn extreme value analysis of the last century crises across industries in the U.S. economyAbstract The two large scale crises that hit the world economy in the last century, i.e. the Great Depression and the Great Recession, have similar outbreak and recovery patterns with respect to several macroeconomic variables. In particular, the largest depressions are likely to be accompanied by stock-market crashes. This study investigates the behavior of the U.S. stock market before, during and after deep downturns, focusing particularly on the tails of the return distribution. We develop two automatic procedures to identify multiple change-points in the tail of financial time series as well as in the co-crash and co-boom probabilities of different markets. We then apply our methodology to twelve time series representative of the sectors of the U.S. economy. We find that regime shifts in the lower tail of the distribution tend to co-occur before deep downturns. Our results contribute to a better understanding of the origin and systemic nature of large scale events to make policy interventions more timely and effective.Marco BeeMassimo Riccabonimassimo.riccaboni@imtlucca.itLuca Trapinluca.trapin@imtlucca.it2017-03-10T08:59:24Z2017-03-21T11:08:28Zhttp://eprints.imtlucca.it/id/eprint/3660This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36602017-03-10T08:59:24ZThe Indirect Effects of FDI on Trade: A Network PerspectiveThe relationship between international trade and foreign direct invest-
ment (FDI) is one of the main features of globalization. In this paper
we investigate the effects of FDI on trade from a network perspective,
since FDI takes not only direct but also indirect channels from origin to
destination countries because of firms' incentive to reduce tax burden,
to minimize coordination costs, and to break barriers to market entry.
We use a unique data set of international corporate control as a measure
of stock FDI to construct a corporate control network (CCN) where the
nodes are the countries and the edges are the corporate control relation-
ships. Based on the CCN, the network measures, i.e., the shortest path
length and the communicability, are computed to capture the indirect
channel of FDI. Empirically we find that corporate control has a positive
effect on trade both directly and indirectly. The result is robust with dif-
ferent specifications and estimation strategies. Hence, our paper provides
strong empirical evidence of the indirect effects of FDI on trade. More-
over, we identify a number of interplaying factors such as regional trade
agreements and the region of Asia. We also find that the indirect effects
are more pronounced for manufacturing sectors than for primary sectors
such as oil extraction and agriculture.Rodolfo MetuliniMassimo Riccabonimassimo.riccaboni@imtlucca.itPaolo Sgrignolipaolo.sgrignoli@alumni.imtlucca.itZhen Zhuzhen.zhu@imtlucca.it2017-01-31T10:17:27Z2017-03-21T11:05:23Zhttp://eprints.imtlucca.it/id/eprint/3650This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36502017-01-31T10:17:27ZVirtual Water Trade and Bilateral ConflictsIn light of growing water scarcity, virtual water, or the water embedded in key water-intensive commodities, has been an active area of debate among practitioners and academics alike. As of yet, however, there is no consensus on whether water scarcity affects conflict behavior and we still lack empirical research intending to account for the role of virtual water in affecting the odds of militarized disputes between states. Using quantitative methods and data on virtual water trade, we find that bilateral and multilateral trade openness reduce the probability of war between any given pair of country, which is consistent with the strategic role of this important commodity and the opportunity cost associated with the loss of trade gains. We also find that the substantive effect of virtual water trade is comparable to that of oil and gas, the archetypal natural resources, in determining interstate conflicts’ probability.Enrico De AngelisRodolfo MetuliniVincenzo BoveMassimo Riccabonimassimo.riccaboni@imtlucca.it2016-10-06T14:27:01Z2016-10-06T14:27:01Zhttp://eprints.imtlucca.it/id/eprint/3572This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/35722016-10-06T14:27:01ZLearning from successes and failures in pharmaceutical R&DIn this paper, we build a cumulative innovation model to understand the role of both success and failure in the learning dynamics that characterize pharmaceutical R&D. We test the prediction of our model by means of a unique dataset that combines patent information with R&D projects, thus distinguishing patents related to successfully marketed products from those covering candidate drugs that failed in clinical trials. Results confirm model predictions showing that patents associated with successfully completed projects receive more citations than those associated with failed projects. However, we also show that failed projects can be in turn cited more often than patents lacking clinical or preclinical information. We further explore the `black box' of innovation, providing evidence that both successes and failures contribute to R&D investment decisions and knowledge dynamics in science-driven sectors.Jing-Yuan ChiouLaura MagazziniFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2016-10-06T14:19:46Z2016-10-06T14:19:46Zhttp://eprints.imtlucca.it/id/eprint/3571This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/35712016-10-06T14:19:46ZReal Options and Incremental Search in Pharmaceutical R&D Project Portfolio ManagementThis paper investigates the role of real options reasoning in R&D project portfolio management and investment decisions of pharmaceutical firms. We analyse a unique dataset that integrates information on initiation and termination of clinical trials at the level of specific medical indications. Consistent with existing literature, we find a positive relationship between market size and firm entry in clinical trials. We also show that the option value of R&D investments, as proxied by the scope of R&D projects, affects the selection of target markets. Moreover, high-risk research areas attract more entry, in line with the predictions of real options theory. However, we also find that more flexibility in project duration and delayed project discontinuation attract higher rates of entry. Departures from pure real options reasoning are motivated by the presence of incremental learning in pharmaceutical R&D.Laura MagazziniFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2016-05-11T10:39:38Z2016-05-11T10:39:38Zhttp://eprints.imtlucca.it/id/eprint/3484This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/34842016-05-11T10:39:38ZThe Water Suitcase of Migrants: Assessing Virtual Water Fluxes Associated to Human MigrationDisentangling the relations between human migrations and water resources is relevant for food security and trade policy in water-scarce countries. It is commonly believed that human migrations are beneficial to the water endowments of origin countries for reducing the pressure on local resources. We show here that such belief is over-simplistic. We reframe the problem by considering the international food trade and the corresponding virtual water fluxes, which quantify the water used for the production of traded agricultural commodities. By means of robust analytical tools, we show that migrants strengthen the commercial links between countries, triggering trade fluxes caused by food consumption habits persisting after migration. Thus migrants significantly increase the virtual water fluxes and the use of water in the countries of origin. The flux ascribable to each migrant, i.e. the "water suitcase", is found to have increased from 321 m3/y in 1990 to 1367 m3/y in 2010. A comparison with the water footprint of individuals shows that where the water suitcase exceeds the water footprint of inhabitants, migrations turn out to be detrimental to the water endowments of origin countries, challenging the common perception that migrations tend to relieve the pressure on the local (water) resources of origin countries.Rodolfo MetuliniStefania TameaFrancesco LaioMassimo Riccabonimassimo.riccaboni@imtlucca.it2016-02-29T10:02:43Z2016-02-29T10:02:43Zhttp://eprints.imtlucca.it/id/eprint/3159This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/31592016-02-29T10:02:43ZAn extreme value analysis of the last century crises
across industries in the U.S. economyThe two large scale crises that hit the world economy in the last century, i.e. the Great
Depression and the Great Recession, have similar outbreak and recovery patterns with
respect to several macroeconomic variables. In particular, the largest depressions are
likely to be accompanied by stock-market crashes. This study investigates the behavior
of the U.S. stock market before, during and after deep downturns, focusing particularly
on the tails of the return distribution. We develop two automatic procedures to identify
multiple change-points in the tail of financial time series as well as in the co-crash and
co-boom probabilities of different markets. We then apply our methodology to twelve
time series representative of the sectors of the U.S. economy. We find that regime
shifts in the lower tail of the distribution tend to co-occur before deep downturns. Our
results contribute to a better understanding of the origin and systemic nature of large
scale events to make policy interventions more timely and effective.Marco BeeMassimo Riccabonimassimo.riccaboni@imtlucca.itLuca Trapinluca.trapin@imtlucca.it2015-11-02T14:47:45Z2015-11-02T14:47:45Zhttp://eprints.imtlucca.it/id/eprint/2804This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/28042015-11-02T14:47:45ZBig hits, export concentration and volatilityRecent empirical work has documented the high concentration of trade flows, and the large role played by few “big hits” in each country’s export. We propose a simple stochastic benchmark against which we assess each economy’s actual number of “big hits”. We show that most European countries underperform the benchmark, while China, the US and Germany do better. A low number of “big hits” (relative to our prediction) is associated with higher export volatility. Looking at possible determinants of “big hits”, we find they depend on the actual performance of each country, so that industrial policy needs to be country-specific.ShamnaazB. SufraujStefano SchiavoMassimo Riccabonimassimo.riccaboni@imtlucca.it2015-09-30T07:39:33Z2015-09-30T07:39:33Zhttp://eprints.imtlucca.it/id/eprint/2753This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/27532015-09-30T07:39:33ZThe Similarity of Global Value Chains: a Network-Based MeasureInternational trade has been increasingly organized in the form of global value chains
(GVCs) where different stages of production are located in dfferent countries. This
recent phenomenon has substantial consequences for both trade policy design at the
national or regional level and business decision making at the form level. In this paper,
we provide a new method for comparing GVCs across countries and over time. First,
we use the World Input-Output Database (WIOD) to construct both the upstream and
downstream global value networks, where the nodes are individual sectors in dfferent
countries and the links are the value-added contribution relationships. Second, we introduce
a network-based measure of node similarity to compare the GVCs between any
pair of countries for each sector and each year available in the WIOD. Our networkbased
similarity is a better measure for node comparison than the existing ones because
it takes into account all the direct and indirect relationships between country-sector
pairs, is applicable to both directed and weighted networks with self-loops, and takes
into account externally defined node attributes. As a result, our measure of similarity
reveals the most intensive interactions among the GVCs across countries and over time.
From 1995 to 2011, the average similarity between sectors and countries have clear increasing
trends, which are temporarily interrupted by the recent economic crisis. This
measure of the similarity of GVCs provides quantitative answers to important questions
about dependency, sustainability, risk, and competition in the global production
system.Zhen Zhuzhen.zhu@imtlucca.itGreg Morrisongreg.morrison@imtlucca.itMichelangelo Puligamichelangelo.puliga@imtlucca.itAlessandro Chessaalessandro.chessa@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2015-08-24T09:09:09Z2015-08-24T09:09:09Zhttp://eprints.imtlucca.it/id/eprint/2737This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/27372015-08-24T09:09:09ZWorld input-output networkProduction systems, traditionally analyzed as almost independent national systems, are increasingly connected on a global scale. Only recently becoming available, the World Input-Output Database (WIOD) is one of the first efforts to construct the global multi-regional input-output (GMRIO) tables. By viewing the world input-output system as an interdependent network where the nodes are the individual industries in different economies and the edges are the monetary goods flows between industries, we analyze respectively the global, regional, and local network properties of the so-called world input-output network (WION) and document its evolution over time. At global level, we find that the industries are highly but asymmetrically connected, which implies that micro shocks can lead to macro fluctuations. At regional level, we find that the world production is still operated nationally or at most regionally as the communities detected are either individual economies or geographically well defined regions. Finally, at local level, for each industry we compare the network-based measures with the traditional methods of backward linkages. We find that the network-based measures such as PageRank centrality and community coreness measure can give valuable insights into identifying the key industries.Federica CerinaZhen Zhuzhen.zhu@imtlucca.itAlessandro Chessaalessandro.chessa@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2015-05-21T09:39:15Z2015-05-21T09:39:15Zhttp://eprints.imtlucca.it/id/eprint/2696This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/26962015-05-21T09:39:15ZStochastic trade networksThis paper develops a simple network model to describe the dynamics of international trade flows. The result is achieved by means of the combination of two mechanisms of proportional growth: the first determines the formation of trade links (intensive margin of trade) and the second governs trade intensity (extensive margin of trade). With respect to recent network models of trade, our approach better fits the numbers of zeros and the degree distribution at different levels of aggregation from firms to national economies. Furthermore, we match a number of additional empirical regularities such as the high concentration of trade with respect to both products and destinations, and the relationship between node degree and node strength. These findings suggest that stylized facts are strongly interconnected across different levels of aggregation, so that a unifying explanation is called for. Our network model can be employed as a useful stochastic benchmark, similar to a generalized gravity model for both trade margins. Massimo Riccabonimassimo.riccaboni@imtlucca.itStefano Schiavo2015-05-20T12:04:10Z2015-05-20T12:04:10Zhttp://eprints.imtlucca.it/id/eprint/2689This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/26892015-05-20T12:04:10ZGlobal Value TreesThe fragmentation of production across countries has become an important feature of the
globalization in recent decades and is often conceptualized by the term “global value chains” (GVCs). When empirically investigating the GVCs, previous studies are mainly in-
terested in knowing how global the GVCs are rather than how the GVCs look like. From a
complex networks perspective, we use the World Input-Output Database (WIOD) to study
the evolution of the global production system. We find that the industry-level GVCs are in-
deed not chain-like but are better characterized by the tree topology. Hence, we compute
the global value trees (GVTs) for all the industries available in the WIOD. Moreover, we
compute an industry importance measure based on the GVTs and compare it with other net-
work centrality measures. Finally, we discuss some future applications of the GVTs.Zhen Zhuzhen.zhu@imtlucca.itMichelangelo Puligamichelangelo.puliga@imtlucca.itFederica CerinaAlessandro Chessaalessandro.chessa@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2015-05-20T11:16:59Z2016-04-07T10:09:10Zhttp://eprints.imtlucca.it/id/eprint/2691This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/26912015-05-20T11:16:59ZThe relation between global migration and trade networksIn this paper we develop a methodology to analyze and compare multiple global networks, focusing our analysis on the relation between human migration and trade. First, we identify the subset of products for which the presence of a community of migrants significantly increases trade intensity, where to assure comparability across networks we apply a hypergeometric filter that lets us identify those links which intensity is significantly higher than expected. Next, proposing a new way to define country neighbors based on the most intense links in the trade network, we use spatial econometrics techniques to measure the effect of migration on international trade, while controlling for network interdependences. Overall, we find that migration significantly boosts trade across countries and we are able to identify product categories for which this effect is particularly strong.Paolo Sgrignolipaolo.sgrignoli@alumni.imtlucca.itRodolfo Metulinirodolfo.metulini@imtlucca.itStefano SchiavoMassimo Riccabonimassimo.riccaboni@imtlucca.it2015-05-20T09:02:03Z2015-05-22T07:42:39Zhttp://eprints.imtlucca.it/id/eprint/2690This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/26902015-05-20T09:02:03ZFrom La Bohème to La Wally: How Organizational Status
Affects the (Un)conventionality of Opera Repertoires
In this paper we examine the relationship between organizational status and nonconformity in complex institutional fields characterized by the enduring tension between divergent institutional logics. First, we hypothesize the existence of an inverted U-shaped (IUS) relationship between status and nonconformity. Second, we argue that legitimacy and celebrity enhancing signals, that complement the external perception of a firm’s market identity, moderate the relationship between status and nonconformity, by springing up or inhibiting opportunities for firms to protect vs. raise their status position through high status patterns of affiliations. Specifically, we argue that while celebrity enhancing efforts reinforce middle status nonconformist behaviors by emphasizing the exceptional and positive valence of their nonconformist undertakings, legitimacy enhancing signals constraint middle status deviant behaviors and reverse the IUS curve. Unveiling the taken-for-granted traits of their identities hampers middle status ambition to raise the social hierarchy through nonconformity but fosters low and high status freedom of deviance through a reinforced security in their social position. We found strong support for our arguments in statistical analysis of 42 Italian opera houses repertoires from 2004 to 2011.
We synthesize our findings by offering an integrated framework on how the interplay between status, legitimacy and celebrity enhancing signals affects organizations’ ability to depart from established institutional frameworks under conditions of institutional complexity.Giulia Cancellierigiulia.cancellieri@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2015-05-18T15:45:57Z2015-11-02T13:13:29Zhttp://eprints.imtlucca.it/id/eprint/2680This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/26802015-05-18T15:45:57ZIdentifying geographic clusters: A network analytic approachIn recent years there has been a growing interest in the role of networks and clusters in the global economy. Despite being a popular research topic in economics, sociology and urban studies, geographical clustering of human activity has often been studied by means of predetermined geographical units, such as administrative divisions and metropolitan areas. This approach is intrinsically time invariant and it does not allow one to differentiate between different activities. Our goal in this paper is to present a new methodology for identifying clusters, that can be applied to different empirical settings. We use a graph approach based on k-shell decomposition to analyze world biomedical research clusters based on PubMed scientific publications. We identify research institutions and locate their activities in geographical clusters. Leading areas of scientific production and their top performing research institutions are consistently identified at different geographic scales.Roberto Catiniroberto.catini@imtlucca.itDmytro Karamshukdmytro.karamshuk@imtlucca.itOrion Pennerorion.penner@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2015-05-05T12:20:47Z2017-05-09T09:27:37Zhttp://eprints.imtlucca.it/id/eprint/2667This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/26672015-05-05T12:20:47ZHomophily and Triadic Closure in Evolving Social NetworksWe present a new network model accounting for homophily and triadic closure in the evolution of social networks. In particular, in our model, each node is characterized by a number of features and the probability of a link between
two nodes depends on common features. The bipartite network of the actors and features evolves according to a dynamics that depends on three parameters that respectively regulate the preferential attachment in the transmission
of the features to the nodes, the number of new features per node, and the power-law behavior of the total number of observed features. We provide theoretical results and statistical estimators for the parameters of the model.
We validate our approach by means of simulations and an empirical analysis of a network of scientifc collaborations.Irene Crimaldiirene.crimaldi@imtlucca.itMichela Del Vicariomichela.delvicario@imtlucca.itGreg Morrisongreg.morrison@imtlucca.itWalter Quattrociocchiwalter.quattrociocchi@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2015-02-18T09:23:46Z2015-02-18T09:23:46Zhttp://eprints.imtlucca.it/id/eprint/2609This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/26092015-02-18T09:23:46ZThe evolution of networks of innovators within and across borders: Evidence from patent data Recent studies on the geography of knowledge networks have documented a negative impact of physical distance and institutional borders upon research and development (R&D) collaborations. Though it is widely recognized that geographic constraints and national borders impede the diffusion of knowledge, less attention has been devoted to the temporal evolution of these constraints. In this study we use data on patents filed with the European Patent Office (EPO) for {OECD} countries to analyze the impact of physical distance and country borders on inter-regional links in four different networks over the period 1988–2009: (1) co-inventorship, (2) patent citations, (3) inventor mobility and (4) the location of R&D laboratories. We find the constraint imposed by country borders and distance decreased until mid-1990s then started to grow, particularly for distance. The intensity of European cross-country inventor collaborations increased at a higher pace than their non-European counterparts until 2004, with no significant relative progress thereafter. For geographical networks of mobility, R&D activities and patent citations we cannot detect any substantial progress in European research integration above and beyond the common global trend. Andrea MorescalchiFabio Pammollif.pammolli@imtlucca.itOrion Pennerorion.penner@imtlucca.itAlexander M. Petersenalexander.petersen@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2015-01-29T08:42:51Z2017-04-03T12:04:07Zhttp://eprints.imtlucca.it/id/eprint/2548This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/25482015-01-29T08:42:51ZSystemic risk and banking regulation: some facts on the new regulatory frameworkThe recent financial crisis highlighted the relevant role of the systemic effects of banks’ defaults on the stability of the whole financial system. In this work we draw an organic picture of the current regulations, moving from the definitions of systemic risk to the issues concerning data availability. We show how a more detailed flow of data on traded deals might shed light on some systemic risk features
taken into account only partially in the past. In particular, we analyse how the new regulatory framework allows regulators to describe OTC derivatives markets according to more detailed partitions, thus depicting a more realistic picture of the system. Finally, we suggest to study submarkets illiquidity conditions to consider possible spill over effects which might lead to a worsening
for the entire system.Michele Bonollomichele.bonollo@imtlucca.itIrene Crimaldiirene.crimaldi@imtlucca.itAndrea Floriandrea.flori@imtlucca.itFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2015-01-12T10:55:20Z2015-01-29T08:42:25Zhttp://eprints.imtlucca.it/id/eprint/2455This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/24552015-01-12T10:55:20ZSystemic risk and banking regulation: some facts on the new regulatory frameworkThe recent financial crisis highlighted the relevant role of the systemic effects of banks’ defaults on the stability of the whole financial system. In this work we draw an organic picture of the current regulations, moving from the definitions of systemic risk to the issues concerning data availability. We show how a more detailed flow of data on traded deals might shed light on some systemic risk features taken into account only partially in the past. In particular, we analyse how the new regulatory framework allows regulators to describe OTC derivatives markets according to more detailed partitions, thus depicting a more realistic picture of the system. Finally, we suggest to study sub-markets illiquidity conditions to consider possible spill over effects which might lead to a worsening for the entire system.Michele Bonollomichele.bonollo@imtlucca.itIrene Crimaldiirene.crimaldi@imtlucca.itAndrea Floriandrea.flori@imtlucca.itFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-11-17T11:38:14Z2014-11-17T11:38:14Zhttp://eprints.imtlucca.it/id/eprint/2370This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/23702014-11-17T11:38:14ZReputation and impact in academic careersReputation is an important social construct in science, which enables informed quality assessments of both publications and careers of scientists in the absence of complete systemic information. However, the relation between reputation and career growth of an individual remains poorly understood, despite recent proliferation of quantitative research evaluation methods. Here, we develop an original framework for measuring how a publication’s citation rate Δc depends on the reputation of its central author i, in addition to its net citation count c. To estimate the strength of the reputation effect, we perform a longitudinal analysis on the careers of 450 highly cited scientists, using the total citations Ci of each scientist as his/her reputation measure. We find a citation crossover c×, which distinguishes the strength of the reputation effect. For publications with c < c×, the author’s reputation is found to dominate the annual citation rate. Hence, a new publication may gain a significant early advantage corresponding to roughly a 66% increase in the citation rate for each tenfold increase in Ci. However, the reputation effect becomes negligible for highly cited publications meaning that, for c ≥ c×, the citation rate measures scientific impact more transparently. In addition, we have developed a stochastic reputation model, which is found to reproduce numerous statistical observations for real careers, thus providing insight into the microscopic mechanisms underlying cumulative advantage in science. Alexander M. Petersenalexander.petersen@imtlucca.itSanto FortunatoRaj K. PanKimmo KaskiOrion Pennerorion.penner@imtlucca.itArmando Rungiarmando.rungi@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itH. Eugene StanleyFabio Pammollif.pammolli@imtlucca.it2014-10-20T13:11:24Z2014-10-20T13:11:24Zhttp://eprints.imtlucca.it/id/eprint/2325This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/23252014-10-20T13:11:24ZGlobal value treesThe fragmentation of production across countries has become an important feature of the globalization in recent decades and is often conceptualized by the term, global value chains (GVCs). When empirically investigating the GVCs, previous studies are mainly interested in knowing how global
the GVCs are rather than how the GVCs look like. From a complex networks perspective, we use the World Input-Output Database (WIOD) to study the global production system. We find that the industry-level GVCs are indeed not chain-like but are better characterized by the tree topology. Hence, we compute the global value trees (GVTs) for all the industries available in the WIOD. Moreover, we compute an industry importance measure based on the GVTs and compare it with other network centrality measures. Finally, we discuss some future applications of the GVTs.Zhen Zhuzhen.zhu@imtlucca.itMichelangelo Puligamichelangelo.puliga@imtlucca.itFederica CerinaAlessandro Chessaalessandro.chessa@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-10-14T09:21:06Z2014-10-27T10:33:58Zhttp://eprints.imtlucca.it/id/eprint/2324This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/23242014-10-14T09:21:06ZCluster analysis of weighted bipartite networks: a new copula-based approachIn this work we are interested in identifying clusters of “positional equivalent” actors, i.e. actors who play a similar role in a system. In particular, we analyze weighted bipartite networks that describes the relationships between actors on one side and features or traits on the other, together with the intensity level to which actors show their features. We develop a methodological approach that takes into account the underlying multivariate dependence among groups of actors. The idea is that positions in a network could be defined on the basis of the similar intensity levels that the actors exhibit in expressing some features, instead of just considering relationships that actors hold with each others. Moreover, we propose a new clustering procedure that exploits the potentiality of copula functions, a mathematical instrument for the modelization of the stochastic dependence structure. Our clustering algorithm can be applied both to binary and real-valued matrices. We validate it with simulations and applications to real-world data.Alessandro Chessaalessandro.chessa@imtlucca.itIrene Crimaldiirene.crimaldi@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itLuca Trapinluca.trapin@imtlucca.it2014-09-10T10:37:54Z2014-09-26T07:12:56Zhttp://eprints.imtlucca.it/id/eprint/2282This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22822014-09-10T10:37:54ZSystemic importance of financial institutions: from a global to a local perspective? A network theory approachAfter the systemic effects of bank defaults during the recent financial crisis, and despite a huge
amount of literature over the last years to detect systemic risk, no standard methodologies have been set up
until now. We aim to build a concise but comprehensive picture of the state of the art, illustrating the open
issues, and outlining pathways for future research. In particular, we propose the analysis of some examples
of local systems that attract the attention of the financial sector. This work is directed to both academic
researchers and practitioners.Michele BonolloIrene Crimaldiirene.crimaldi@imtlucca.itAndrea Floriandrea.flori@imtlucca.itFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-09-02T12:17:12Z2014-12-05T10:10:15Zhttp://eprints.imtlucca.it/id/eprint/2278This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22782014-09-02T12:17:12ZPreferential attachment in multiple trade networksIn this paper we develop a model for the evolution of multiple networks which is able to replicate the concentrated and sparse nature of world trade data. Our model is an extension of the preferential attachment growth model to the case of multiple networks. Countries trade a variety of goods of different complexity. Every country progressively evolves from trading less sophisticated to high-tech goods. The probabilities of capturing more trade opportunities at a given level of complexity and of starting to trade more complex goods are both proportional to the number of existing trade links. We provide a set of theoretical predictions and simulative results. A calibration exercise shows that our model replicates the same concentration level of world trade as well as the sparsity pattern of the trade matrix. We also discuss a set of numerical solutions to deal with large multiple networks.Rachele FoschiMassimo Riccabonimassimo.riccaboni@imtlucca.itStefano Schiavo2014-09-02T10:30:20Z2015-04-21T08:20:39Zhttp://eprints.imtlucca.it/id/eprint/2274This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22742014-09-02T10:30:20ZBorder sensitive centrality in global patent citation networksWhen resources are shared between interacting networks, the importance of each node depends strongly on how collaborative or competitive each sub-network is. In this paper, we develop a new method of measuring centrality in the complex network of patent citations that can take political borders into account, where the national benefit of domestic citations relative to foreign citations can be controlled by a free parameter. We find that while some patent classes are of high importance both in the global and the domestic economy, there often exist patent classes in individual countries that are more central nationally than in global economy. We characterize the most important classes globally and domestically for six different nations, and describe their robustness to various perturbations to the model and to noise. Greg Morrisongreg.morrison@imtlucca.itEleftherios GiovanisFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-09-01T12:17:22Z2014-09-01T13:08:11Zhttp://eprints.imtlucca.it/id/eprint/2271This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22712014-09-01T12:17:22ZThe rise of China in the international trade network: a community core detection approachTheory of complex networks proved successful in the description of a variety of complex systems ranging from biology to computer science and to economics and finance. Here we use network models to describe the evolution of a particular economic system, namely the International Trade Network (ITN). Previous studies often assume that globalization and regionalization in international trade are contradictory to each other. We re-examine the relationship between globalization and regionalization by viewing the international trade system as an interdependent complex network. We use the modularity optimization method to detect communities and community cores in the ITN during the years 1995–2011. We find rich dynamics over time both inter- and intra-communities. In particular, the Asia-Oceania community disappeared and reemerged over time along with a switch in leadership from Japan to China. We provide a multilevel description of the evolution of the network where the global dynamics (i.e., communities disappear or reemerge) and the regional dynamics (i.e., community core changes between community members) are related. Moreover, simulation results show that the global dynamics can be generated by a simple dynamic-edge-weight mechanism.Zhen Zhuzhen.zhu@imtlucca.itFederica CerinaAlessandro Chessaalessandro.chessa@imtlucca.itGuido Caldarelliguido.caldarelli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-08-05T09:07:30Z2014-08-05T09:07:30Zhttp://eprints.imtlucca.it/id/eprint/2269This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22692014-08-05T09:07:30ZGlobal Virtual Water Trade: integrating Structural
Decomposition Analysis with Network TheoryThe consideration of both the direct and the indirect effects of global production and trade is the first step in order to assess the sustainability of resource exploitation, in particular water usage. This paper
applies the Global Multi-Regional Input-Output model to quantify the interdependencies of different sectors
and to determine the overall water consumption of each country. This procedure allows the measurement of Virtual Water Trade, that is the volume of water embedded in traded goods. This paper introduces further extensions based on network analysis to overcome the limitations of I-O models. To the best of our knowledge, this is the first attempt to build a bridge between two different, but related, methodologies. Firstly, we assess the evolution of the structure of international trade in Virtual Water (VW). Secondly, we present the results from the Structural Decomposition Analysis. Finally, we introduce other measures
from Network Theory, in order to integrate the previous results. Community Detection assessment reveals
the emergence of regional VW systems composed by a limited set of countries. Thus our study confirms the need of elaborating and implementing transboundary policies for water management, especially in the European Union.Tiziano Distefanotiziano.distefano@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itGiovanni Maringiovanni.marin@alumni.imtlucca.it2014-07-03T13:33:27Z2014-07-03T13:33:27Zhttp://eprints.imtlucca.it/id/eprint/2246This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22462014-07-03T13:33:27ZSmall firms and technological change in markets for technology. The pharmaceutical industry after the revolution in molecular biologyFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-07-03T12:57:47Z2014-07-03T12:57:47Zhttp://eprints.imtlucca.it/id/eprint/2245This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22452014-07-03T12:57:47ZA generalized preferential attachment model for complex systemsComplex systems can be characterized by classes of equivalency of their elements defined according to system specific rules. We propose a generalized preferential attachment model to describe the class size distribution. The model postulates preferential growth of the existing classes and the steady influx of new classes. We investigate how the distribution depends on the initial conditions and changes from a pure exponential form for zero influx of new classes to a power law with an exponential cutoff form when the influx of new classes is substantial. We apply the model to study the growth dynamics of pharmaceutical industry. Kazuko YamasakiKaushik MatiaDongfeng FuSergey V. BuldyrevFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itH. Eugene Stanley2014-07-03T12:51:09Z2014-07-03T12:59:41Zhttp://eprints.imtlucca.it/id/eprint/2244This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22442014-07-03T12:51:09ZCompetencies, technological change and network dynamics. The case of the bio-pharmaceutical industryLuigi OrsenigoFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-07-03T12:40:30Z2016-04-06T09:47:26Zhttp://eprints.imtlucca.it/id/eprint/2243This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22432014-07-03T12:40:30ZI Farmaci Oncologici in Italia: innovazione e sostenibilità economicaI farmaci innovativi ad alto costo ci fanno toccare con mano quali potranno essere i dilemmi della sanità futura se non si completano le riforme della governance di questo capitolo complesso della spesa pubblica (non solo federalismo, ma sistemi contabili e di reporting, schemi di compartecipazione al costo, screening delle prassi terapeutiche per sollecitare best practice, etc.). Quel trade-off crudo che abbiamo di fronte, tra sostenibilità della spesa e domanda di prestazioni da parte dei cittadini, è, per i farmaci ad alto costo, già una realtà vissuta in tutti gli ospedali. Nella prima parte del rapporto Pammolli, Riccaboni e Salerno descrivono le caratteristiche del comparto, fornendone le grandezze principali attuali e prospettiche, anche in chiave di comparazione internazionale. Nella seconda parte, gli autori approfondiscono il quadro normativo-regolatorio che attualmente presiede alla governance dei farmaci oncologici in Italia. Ne emerge un sistema con ombre e approssimazioni, con impostazioni diverse e spesso incompatibili tra Aifa e Regioni, tra Regione e Regione, addirittura tra Als e Ospedali di una stessa Regione. Un assetto poco trasparente e certo non pronto a governare in maniera positiva e programmatica la forbice tra risorse spendibili e necessità e urgenza delle terapie. Nella parte conclusiva del rapporto si avanzano alcune proposte di policy, distinguendo tra quelle attuabili in tempi brevi e quelle per le quali sono necessari tempi di attuazione più lunghi. Le due tipologie di intervento andrebbero avviate il prima possibile e auspicabilmente condotte in parallelo.Fabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itNicola C. Salerno2014-07-03T12:17:44Z2016-04-06T09:47:39Zhttp://eprints.imtlucca.it/id/eprint/2242This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22422014-07-03T12:17:44ZLa spesa farmaceutica territoriale convenzionata: il modello FarmaRegio per l'analisi della variabilità regionaleSi presenta la prima versione di FarmaRegio, modello econometrico per l'analisi della variabilità regionale della spesa farmaceutica territoriale convenzionata (un panel ad effetti casuali). Si suggeriscono due prospettive di lettura: da un lato, la valutazione della significatività delle variabili esplicative; dall'altro, l'interpretazione della relazione funzionale stimata come possibile benchmark con cui chiedere alle Regioni di confrontarsi. Nel primo caso, emergono chiare indicazioni di policy: la rilevanza del reddito e quindi dei flussi di perequazione a sostegno dei LEA, ma anche l'importanza degli strumenti di regolazione lato offerta/domanda, e delle riforme pro concorrenziali della distribuzione al dettaglio. Poco significativo appare l'impatto dell'invecchiamento, la qual cosa dovrebbe far riflettere sul peso da assegnare a questa variabile nell'allocazione interregionale delle risorse oppure, nel caso in cui il risultato derivasse da razionamenti dell'offerta, sull'utilità di ripristinare vincoli di destinazione mirati su una selezione di prestazioni. Nel secondo caso, la relazione funzionale media può concorrere a dare concretezza a quel riferimento ai costi standard dei LEA presente anche nel recente disegno di legge applicativo dell'articolo 119 della Costituzione.Chiara BonassiLaura MagazziniFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itNicola C. Salerno2014-07-02T09:01:07Z2017-01-13T10:13:02Zhttp://eprints.imtlucca.it/id/eprint/2230This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22302014-07-02T09:01:07ZWorld input-output networkEconomic systems, traditionally analyzed as almost independent national systems, are increasingly connected on a global scale. Only recently becoming available, the World Input-Output Database (WIOD) is one of the first efforts to construct the multi-regional input-output (MRIO) tables at the global level. By viewing the world input-output system as an interdependent network where the nodes are the individual industries in different economies and the edges are the monetary goods flows between industries, we study the network properties of the so-called world input-output network (WION) and document its evolution over time. We are able to quantify not only some global network properties such as assortativity, clustering coefficient, and degree and strength distributions, but also its subgraph structure and dynamics by using community detection techniques. Over time, we detect a marked increase in cross-country connectivity of the production system, only temporarily interrupted by the 2008-2009 crisis. Moreover, we find a growing input-output regional community in Europe led by Germany and the rise of China in the global production system. Finally, we use the network-based PageRank centrality and community coreness measure to identify the key industries and economies in the WION and the results are different from the one obtained by the traditional final-demand-weighted backward linkage measure. Federica CerinaZhen Zhuzhen.zhu@imtlucca.itAlessandro Chessaalessandro.chessa@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-05-13T09:07:10Z2014-07-07T10:27:41Zhttp://eprints.imtlucca.it/id/eprint/2196This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/21962014-05-13T09:07:10ZA multi-level geographical study of Italian political elections from Twitter DataIn this paper we present an analysis of the behavior of Italian Twitter users during national political elections. We monitor the volumes of the tweets related to the leaders of the various political parties and we compare them to the elections results. Furthermore, we study the topics that are associated with the co-occurrence of two politicians in the same tweet. We cannot conclude, from a simple statistical analysis of tweet volume and their time evolution, that it is possible to precisely predict the election outcome (or at least not in our case of study that was characterized by a “too-close-to-call” scenario). On the other hand, we found that the volume of tweets and their change in time provide a very good proxy of the final results. We present this analysis both at a national level and at smaller levels, ranging from the regions composing the country to macro-areas (North, Center, South).Guido Caldarelliguido.caldarelli@imtlucca.itAlessandro Chessaalessandro.chessa@imtlucca.itFabio Pammollif.pammolli@imtlucca.itGabriele Pompagabriele.pompa@imtlucca.itMichelangelo Puligamichelangelo.puliga@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itGianni Riotta2014-05-06T13:34:39Z2014-07-28T09:34:36Zhttp://eprints.imtlucca.it/id/eprint/2193This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/21932014-05-06T13:34:39ZThe migration network effect on international tradeThis paper studies the relationship between migration and trade, with the aim of measuring both direct and indirect network effects. We analyze trade of diferentiated and homogeneous goods using an econometric approach inspired by spatial econometrics, proposing a new way to define country neighbors based on the most
intense links in the migration network. We find that migration significantly affects trade across categories both in direct and in indirect way. The indirect impact
highlights a stronger competitive effect of third country migrants for homogeneous goods. We also confirm that the effect of migration channels is higher on differentiated goods.Rodolfo Metulinirodolfo.metulini@imtlucca.itPaolo Sgrignolipaolo.sgrignoli@alumni.imtlucca.itStefano SchiavoMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-04-29T08:36:57Z2014-04-29T08:36:57Zhttp://eprints.imtlucca.it/id/eprint/2192This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/21922014-04-29T08:36:57ZThe rise of China in the international trade network: a community core detection approachTheory of complex networks proved successful in the description of a variety of static networks ranging from biology to computer and social sciences and to economics and
finance. Here we use network models to describe the evolution of a particular economic system, namely the International Trade Network (ITN). Previous studies often assume that globalization and regionalization in international trade are contradictory to each other. We re-examine the relationship between globalization and regionalization by viewing the international trade system as an interdependent complex network. We use the modularity optimization method to detect communities and community cores in the ITN during the years 1995-2011. We find rich dynamics over time both inter- and intra-communities. Most importantly, we have a multilevel description of the
evolution where the global dynamics (i.e., communities disappear or reemerge) tend to be correlated with the regional dynamics (i.e., community core changes between
community members). In particular, the Asia-Oceania community disappeared and reemerged over time along with a switch in leadership from Japan to China. Moreover,
simulation results show that the global dynamics can be generated by a preferential attachment mechanism both inter- and intra- communities. Zhen Zhuzhen.zhu@imtlucca.itFederica CerinaAlessandro Chessaalessandro.chessa@imtlucca.itGuido Caldarelliguido.caldarelli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-04-10T12:19:02Z2014-10-27T10:46:30Zhttp://eprints.imtlucca.it/id/eprint/2189This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/21892014-04-10T12:19:02ZCluster analysis of weighted bipartite networks: a new copula-based approachIn this work we are interested in identifying clusters of "positional equivalent" actors, i.e. actors who play a similar role in a system. In particular, we analyze weighted bipartite networks that describes the relationships between actors on one side and features or traits on the other, together with the intensity level to which actors show their features. The main contribution of our work is twofold. First, we develop a methodological approach that takes into account the underlying multivariate dependence among groups of actors. The idea is that positions in a network could be defined on the basis of the similar intensity levels that the actors exhibit in expressing some features, instead of just considering relationships that actors hold with each others. Second, we propose a new clustering procedure that exploits the potentiality of copula functions, a mathematical instrument for the modelization of the stochastic dependence structure. Our clustering algorithm can be applied both to binary and real-valued matrices. We validate it with simulations and applications to real-world data. Alessandro Chessaalessandro.chessa@imtlucca.itIrene Crimaldiirene.crimaldi@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itLuca Trapinluca.trapin@imtlucca.it2014-04-01T12:19:37Z2014-04-01T12:19:37Zhttp://eprints.imtlucca.it/id/eprint/2188This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/21882014-04-01T12:19:37ZNetwork communities within and across bordersWe investigate the impact of borders on the topology of spatially embedded networks. Indeed territorial subdivisions and geographical borders significantly hamper the geographical span of networks thus playing a key role in the formation of network communities. This is especially important in scientific and technological policy-making, highlighting the interplay between pressure for the internationalization to lead towards a global innovation system and the administrative borders imposed by the national and regional institutions. In this study we introduce an outreach index to quantify the impact of borders on the community structure and apply it to the case of the European and US patent co-inventors networks. We find that (a) the US connectivity decays as a power of distance, whereas we observe a faster exponential decay for Europe; (b) European network communities essentially correspond to nations and contiguous regions while US communities span multiple states across the whole country without any characteristic geographic scale. We confirm our findings by means of a set of simulations aimed at exploring the relationship between different patterns of cross-border community structures and the outreach index.Federica CerinaAlessandro Chessaalessandro.chessa@imtlucca.itFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-03-27T14:26:48Z2014-03-27T14:26:48Zhttp://eprints.imtlucca.it/id/eprint/2186This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/21862014-03-27T14:26:48ZStructure and growth of weighted networksWe develop a simple theoretical framework for the evolution of weighted networks that is consistent with a number of stylized features of real-world data. In our framework, the Barabási–Albert model of network evolution is extended by assuming that link weights evolve according to a geometric Brownian motion. Our model is verified by means of simulations and real-world trade data. We show that the model correctly predicts the intensity and growth distribution of links, the size–variance relationship of the growth of link weights, the relationship between the degree and strength of nodes, and the scale-free structure of the network.Massimo Riccabonimassimo.riccaboni@imtlucca.itStefano Schiavo2014-03-27T14:06:12Z2014-03-27T14:55:59Zhttp://eprints.imtlucca.it/id/eprint/2185This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/21852014-03-27T14:06:12ZSystemic importance of financial institutions: regulations, research, open issues, proposalsIn the field of risk management, scholars began to bring together the quantitative methodologies with the banking management issues about 30 years ago, with a special focus on market, credit and operational risks. After the systemic effects of banks defaults during the recent financial crisis,
and despite a huge amount of literature in the last years concerning the systemic risk, no standard methodologies have been set up to now. Even the new Basel 3 regulation has adopted a heuristic indicator-based approach, quite far from an effective quantitative tool. In this paper, we refer to the different pieces of the puzzle: definition of systemic risk, a set of coherent and useful measures, the computability of these measures, the data set structure. In this challenging field, we aim to build a comprehensive picture of the state of the art, to illustrate the open issues, and to outline some paths for a more successful future research. This work appropriately integrates other useful surveys and it is directed to both academic researchers and practitioners.Michele BonolloIrene Crimaldiirene.crimaldi@imtlucca.itAndrea Floriandrea.flori@imtlucca.itFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-02-04T10:17:30Z2014-03-05T12:05:36Zhttp://eprints.imtlucca.it/id/eprint/2130This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/21302014-02-04T10:17:30ZBorder sensitive centralities in patent citation networks using asymmetric random walksGrowth and innovation in particular sectors of the economy can be spurred by funding from governments or firms with the initial investment producing spillovers into other sectors of the economy. Funding sectors that are central to the economy are expected to produce more or greater spillovers than if more peripheral sectors were funded. If the funding body is a national government, it is desirable that spillovers remain primarily in the domestic economy rather than targeting globally central sectors and risk subsidizing a foreign economy. In this paper, we develop a new method of measuring centrality in the complex network of patent citations that can take national borders into account, where the importance of domestic citations relative to foreign citations can be controlled by a free parameter. We find empirically that while some patent classes are of high importance both in the global and the domestic economy, there often exist patent classes in individual countries that are more central nationally than in global economy.Greg Morrisongreg.morrison@imtlucca.itEleftherios Giovaniseleftherios.giovanis@imtlucca.itFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-01-08T14:33:12Z2014-04-29T10:38:09Zhttp://eprints.imtlucca.it/id/eprint/2085This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/20852014-01-08T14:33:12ZThe evolution of networks of innovators within and across borders: Evidence from patent dataRecent studies on the geography of knowledge networks have documented a negative impact of physical distance and institutional borders upon research and development (R&D) collaborations. Though it is widely recognized that geographic constraints and national borders impede the diffusion of knowledge, less attention has been devoted to the temporal evolution of these constraints. In this study we use data on patents filed with the European Patent Office (EPO) for OECD countries to analyze the impact of physical distance and country borders on inter-regional links in four different networks over the period 1988-2009: (1) co-inventorship, (2) patent citations, (3) inventor mobility and (4) the location of R&D laboratories. We find the constraint imposed by country borders and distance decreased until mid-1990s then started to grow, particularly for distance. We further investigate the role of large innovation "hubs" as attractors of new collaboration opportunities and the impact of region size and locality on the evolution of cross-border patenting activities. The intensity of European cross-country
inventor collaborations increased at a higher pace than their non-European counterparts until 2004,
with no significant relative progress thereafter. Moreover, when analyzing networks of geographical mobility, multinational R&D activities and patent citations we cannot detect any substantial progress in European research integration above and beyond the common global trend.Andrea Morescalchiandrea.morescalchi@imtlucca.itFabio Pammollif.pammolli@imtlucca.itOrion Pennerorion.penner@imtlucca.itAlexander M. Petersenalexander.petersen@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2013-10-09T14:10:24Z2014-07-28T09:34:20Zhttp://eprints.imtlucca.it/id/eprint/1830This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/18302013-10-09T14:10:24ZThe Relation Between Global Migration and Trade NetworksIn this paper we develop a methodology to analyze and compare multiple global networks. We focus our analysis on the relation between human migration and trade. First, we identify the subset of products for which the presence of a community of migrants significantly increases trade intensity. To assure comparability across networks, we apply a hypergeometric filter to identify links for which migration and trade intensity are both significantly
higher than expected. Next we develop an econometric methodology, inspired by spatial econometrics, to measure the effect of migration on international trade while controlling for network interdependencies. Overall,
we find that migration significantly boosts trade across sectors and we are able to identify product categories for
which this effect is particularly strong.Paolo Sgrignolipaolo.sgrignoli@alumni.imtlucca.itRodolfo Metulinirodolfo.metulini@imtlucca.itStefano SchiavoMassimo Riccabonimassimo.riccaboni@imtlucca.it2013-09-10T09:35:32Z2013-09-10T09:35:32Zhttp://eprints.imtlucca.it/id/eprint/1658This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/16582013-09-10T09:35:32ZMissing Links in Multiple Trade NetworksIn this paper we develop a network model of international trade which is able to replicate the concentrated and sparse nature of trade data. Our model extends the preferential attachment (PA) growth model to the case of multiple networks. Countries trade a variety of goods of
different complexity. Every country progressively evolves from trading less sophisticated to high-tech goods. The probability to capture more trade opportunities at a given level of complexity and to start trading more complex goods are both proportional to the number of existing trade links. We provide a set of theoretical predictions and simulative results. A calibration exercise shows that our model replicates the same concentration level of world trade as well as the sparsity pattern of the trade matrix. Moreover, we find a lower bound for the share of genuine missing trade links. We also discuss a set of numerical
solutions to deal with large multiple networks.Rachele Foschirachele.foschi@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itStefano Schiavo2013-08-06T07:40:23Z2013-08-06T07:40:23Zhttp://eprints.imtlucca.it/id/eprint/1654This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/16542013-08-06T07:40:23ZNetworks of innovators within and across borders. Evidence from patent dataRecent studies on the geography of knowledge networks have documented a negative impact of physical distance and institutional borders upon research and development (R&D) collaborations. Though it is widely recognized that geographic constraints hamper the diffusion of knowledge,
less attention has been devoted to the temporal evolution of these constraints. In this study we use data on patents filed with the European Patent Office (EPO) for 50 countries to analyze the impact of physical distance and country borders on inter-regional links in four different networks over the period 1988-2009: (1) co-inventorship, (2) patent citations, (3) inventor mobility and (4)
the location of R&D laboratories. We find the constraint imposed by country borders and distance decreased until mid-1990s then started to grow, particularly for distance. The intensity of European cross-country inventor collaborations increased at a higher pace than their non-European counterparts until 2004, with no significant relative progress afterwards. Moreover, when analyzing
networks of geographical mobility, multinational R&D activities and patent citations we do not depict any substantial progress in European research integration aside from the influence of common global trends.Andrea Morescalchiandrea.morescalchi@imtlucca.itFabio Pammollif.pammolli@imtlucca.itOrion Pennerorion.penner@imtlucca.itAlexander M. Petersenalexander.petersen@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2013-08-05T08:44:36Z2013-08-05T08:44:36Zhttp://eprints.imtlucca.it/id/eprint/1652This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/16522013-08-05T08:44:36ZThe size distribution of US cities: Not Pareto, even in the tail Abstract We question the claim that the largest {US} cities are Pareto distributed. We show that results of multiple tests on real data are similar to those obtained when the true distribution is lognormal, and largely depend on sample sizes. Marco BeeMassimo Riccabonimassimo.riccaboni@imtlucca.itStefano Schiavo2013-07-01T09:02:18Z2013-07-01T09:02:18Zhttp://eprints.imtlucca.it/id/eprint/1625This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/16252013-07-01T09:02:18ZR&D, Within and Between Patent Competition in the Pharmaceutical IndustryWe analyse the consequences of the increasing complexity of R&D on within- and between-patent competition in the pharmaceutical industry. The intensity of competition
is measured by jointly considering the timing from market launch to patent expiry, the strength of between-patent competition as well as competition introduced by generic
producers. A simple model is proposed that predicts the shrinking of product lifetimes in the presence of correlated parallel R&D projects and market portfolios. The model is tested using data on pharmaceutical products sold in Europe and in the US. Based on our model we are able to estimate the impact of R&D complexity and relatedness
among R&D portfolios on the value of innovative drugs.Laura MagazziniFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2013-04-15T13:48:49Z2016-04-07T09:38:58Zhttp://eprints.imtlucca.it/id/eprint/1543This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/15432013-04-15T13:48:49ZEvolution of controllability in interbank networksThe Statistical Physics of Complex Networks has recently provided new theoretical tools for policy makers. Here we extend the notion of network controllability to detect the financial institutions, i.e. the drivers, that are most crucial to the functioning of an interbank market. The system we investigate is a paradigmatic case study for complex networks since it undergoes dramatic structural changes over time and links among nodes can be observed at several time scales. We find a scale-free decay of the fraction of drivers with increasing time resolution, implying that policies have to be adjusted to the time scales in order to be effective. Moreover, drivers are often not the most highly connected “hub” institutions, nor the largest lenders, contrary to the results of other studies. Our findings contribute quantitative indicators which can support regulators in developing more effective supervision and intervention policies.Danilo DelpiniStefano BattistonMassimo Riccabonimassimo.riccaboni@imtlucca.itGiampaolo GabbiFabio Pammollif.pammolli@imtlucca.itGuido Caldarelliguido.caldarelli@imtlucca.it2013-04-02T08:02:20Z2013-04-02T08:02:20Zhttp://eprints.imtlucca.it/id/eprint/1539This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/15392013-04-02T08:02:20ZExperience, socialization and customer retention: Lessons from the dance floorExperience and socialization are key factors in customer commitment and defection decisions. To study the effect of experience and social relationships on customer retention, we analyze a reality-mined co-presence network of health club members over a period of 4 years. Since central customers in the network have more social ties they will lose if they defect, we use centrality as a proxy for customer relationship switching costs. We find that long-standing customers do have a lower chance of renewing their contracts. However, in line with theoretical predictions (Burnham et al., Journal of the Academy of Marketing Science 31(2):109–126, 2003), the consumer’s centrality in the network (reflecting a social cost of defection) reduces customer churn rate. This study’s results indicate that the inclusion of social effects increases the predictive power of the customer churn model (Nitzan and Libai, Journal of Marketing 75(6):24–38, 2011), thus contributing to our understanding of the role social networks play in customer decisions.Gianna GiudicatiMassimo Riccabonimassimo.riccaboni@imtlucca.itAnna Romiti2013-02-13T08:06:14Z2017-04-03T12:17:53Zhttp://eprints.imtlucca.it/id/eprint/1474This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/14742013-02-13T08:06:14ZIs Europe Evolving Toward an Integrated Research Area?Efforts toward European research and development (R&D) integration have a long history, intensifying with the Fifth Framework Programme (FP) in 1998 (1–3) and the launch of the European Research Area (ERA) initiative at the Lisbon European Council in 2000. A key component of the European Union (EU) strategy for innovation and growth (4, 5), the ERA aims to overcome national borders through directed funding, increased mobility, and streamlined innovation policies.Alessandro Chessaalessandro.chessa@imtlucca.itAndrea Morescalchiandrea.morescalchi@imtlucca.itFabio Pammollif.pammolli@imtlucca.itOrion Pennerorion.penner@imtlucca.itAlexander M. Petersenalexander.petersen@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2013-01-22T15:35:01Z2013-01-22T15:52:05Zhttp://eprints.imtlucca.it/id/eprint/1461This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/14612013-01-22T15:35:01ZStochastic Trade NetworksThis paper develops a simple network model to describe the dynamic of the intensive and extensive margin of international trade flows. The result is achieved by means of the combination of two mechanisms of proportional
growth: the first (discrete) determines the formation of trade links, the second (continuous) governs trade intensity. We show that our setup is able to simultaneously match a large number of empirical regularities, such as the
fraction of zero trade flows across pairs of countries or the high concentration of trade with respect to both products and destinations. Our findings suggest that stylized facts are strongly interconnected across different levels of aggregation of trade data , so that a unifying explanation is called for. By incorporating stochastic elements into standard trade models we can improve their ability to explain relevant facts about world trade.Massimo Riccabonimassimo.riccaboni@imtlucca.itStefano Schiavo2012-09-11T08:24:52Z2014-01-13T10:32:53Zhttp://eprints.imtlucca.it/id/eprint/1342This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/13422012-09-11T08:24:52ZGlobal networks of trade and bitsConsiderable efforts have been made in recent years to produce detailed topologies of the Internet, but so far these data have been overlooked by economists. In this paper, we suggest that such information could be used to characterize both the size of the digital economy and outsourcing at country level. We analyse the topological structure of the network of trade in digital services (trade in bits) and compare it with the more traditional flow of manufactured goods across countries. To perform meaningful comparisons across networks with different characteristics, we define a stochastic benchmark for the number of connections among each country-pair, based on hypergeometric distribution. Original data are filtered so that we only focus on the strongest, i.e. statistically significant, links. We find that trade in bits displays a sparser and less hierarchical network structure, which is more similar to trade in high-skill manufactured goods than total trade. Moreover, distance plays a more prominent role in shaping the network of international trade in physical goods than trade in digital services.Massimo Riccabonimassimo.riccaboni@imtlucca.itAlessandro RossiStefano Schiavo2012-04-26T11:07:06Z2012-04-26T11:07:06Zhttp://eprints.imtlucca.it/id/eprint/1265This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/12652012-04-26T11:07:06ZA Trick of the (Pareto) TailSeveral economic phenomena are found to follow an approximate Pareto distribution, at least in the upper tail. The debate is well established for the distribution of wealth and business firms, and has recently been particularly animated with respect to city sizes. In this paper we contribute to this stream of the literature by showing that the power-law tail emerges upon aggregation, and this holds true across three different domains: cities, firms and trade flows. We explore different mechanisms that could give rise to this effect, from mere sample size to correlation among the number of constituent parts of aggregate entities and their size, to the aggregation rule, and discuss their impact on the Pareto tail. Using multiple statistical tests we show that it is impossible to prove the existence of a genuine Pareto tail for the US city size distribution because of the smallness of the number of observations. Furthermore, the presence of a positive power-law relationship between the number of units (products, establishments) comprised in each firm and their average size is key to explain why the size distribution of business firms displays a power-law tail. Conversely, we do not find any Pareto tail for trade flows. The paper casts new light on the mechanisms through which idiosyncratic shocks do not average out upon aggregation, so that individual shocks are not washed away in economic aggregates, as the central limit theorem would predict, but can even be magnified.Marco BeeMassimo Riccabonimassimo.riccaboni@imtlucca.itStefano Schiavo2012-03-02T12:06:48Z2012-03-02T12:06:48Zhttp://eprints.imtlucca.it/id/eprint/1202This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/12022012-03-02T12:06:48ZThe Value of Failures in Pharmaceutical R&DWe build a cumulative innovation model in which both success and failure provide valuable information for future research. To test this learning mechanism, we use a dataset covering outcomes of world-wide R&D projects in the pharmaceutical industry, and proxy knowledge flows with forward citations received by patents associated with each project. Empirical results confirm theoretical predictions that patents associated with successfully completed projects (i.e., leading to drug launch on the market) receive more citations than those associated to failed (terminated) projects, which in turn are cited more often than patents lacking clinical or preclinical information. We therefore offer evidence of the value of failures as research inputs in (pharmaceutical) innovation.Jing-Yuan Chioujy.chiou@imtlucca.itLaura MagazziniFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2012-03-02T11:32:00Z2012-04-19T09:52:31Zhttp://eprints.imtlucca.it/id/eprint/1201This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/12012012-03-02T11:32:00ZLearning from failures or failing to learn? Lessons from pharmaceutical R&DInnovation is a trial and error process in which both successes and failures contribute to knowledge creation and
destruction. In this paper we test theoretical predictions about the role of failures in new product development on
private and public knowledge and interfirm knowledge transfer. We analyse the outcomes of world-wide R&D
projects in the pharmaceutical industry, and proxy knowledge flows with forward citations received by patents
associated with each project. We find that patents covering successfully completed projects (i.e., leading to drug
launch on the market) receive more citations than those associated to failed (terminated) projects, which in turn
are cited more often than patents lacking clinical or preclinical information. Failures by specialized firms are cited more frequently than the ones of generalist companies. We therefore offer evidence of the value of failures as research inputs in (pharmaceutical) innovation.Laura MagazziniFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2012-01-19T13:11:43Z2014-01-24T14:23:18Zhttp://eprints.imtlucca.it/id/eprint/1069This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10692012-01-19T13:11:43ZThe structure and growth of international tradeThe paper develops a model of proportionate growth to describe the dynamics of international trade flows. We show that a large number of the empirical regularities characterizing international trade -such as the fraction of zero trade flows across pairs of countries, the positive relationship between intensive and extensive margins, the high concentration of trade with respect to both products and destinations, the core-periphery structure of exchanges- are well explained by this simple stochastic setup. This helps us to distinguish among economically relevant regularities and those simply resulting from the mechanical interactions among agents. Furthermore, our model can be used to describe the process of `self-discovery' that lie at the foundations of suc- cessful export-led growth and is thought to play a crucial role in the process of economic development. Our model correctly predicts that large export flows are rare events, as pointed out in the empirical literature: yet, countries characterized by large `discovery' efforts are much more likely to draw a `big hit' due to the (very skewed) shape of the distribution of bilateral export flows.Massimo Riccabonimassimo.riccaboni@imtlucca.itStefano Schiavo2012-01-19T12:00:39Z2012-01-19T12:00:39Zhttp://eprints.imtlucca.it/id/eprint/1067This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10672012-01-19T12:00:39ZLa dinamica dei rapporti tra grandi e piccole imprese: alcune riflessioni tra teoria ed analisi storica Giovanni DosiMassimo Riccabonimassimo.riccaboni@imtlucca.itRiccardo Varaldo2012-01-19T11:08:08Z2012-01-19T11:08:08Zhttp://eprints.imtlucca.it/id/eprint/1066This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10662012-01-19T11:08:08ZCambiamento tecnologico e reti di impresePochi concetti come quello di rete hanno avuto un così grande successo, sia negli studi aziendali di matrice strategica, organizzativa, manageriale sia in ambito interdisciplinare nell'analisi della dinamica dei sistemi fisici, biologici e sociali. Il libro adotta una prospettiva di ampio respiro volta ad analizzare l'evoluzione delle reti di collaborazione tra imprese in settori caratterizzati da intense dinamiche innovative. In tempi recenti si è assistito ad un crescente ricorso a pratiche di partnership e di divisione del lavoro innovativo volte a generare, integrare, sviluppare e diffondere competenze scientifico-tecnologiche in diversi settori quali le scienze della vita, dell'informazione, della comunicazione e dei materiali.
Ampiamente argomentato dal punto di vista teorico ed empirico, il tema delle reti innovative è sviluppato nel volume integrando diverse prospettive, con particolare riferimento ai recenti sviluppi dell'analisi industriale e organizzativa dei processi innovativi.Massimo Riccabonimassimo.riccaboni@imtlucca.it2012-01-19T11:01:46Z2012-01-19T11:01:46Zhttp://eprints.imtlucca.it/id/eprint/1065This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10652012-01-19T11:01:46ZLe diversità dell'industria italiana nella nuova integrazione economica internazionaleRiccardo VaraldoNicola BelliniAndrea BonaccorsiMassimo Riccabonimassimo.riccaboni@imtlucca.it2012-01-19T10:38:13Z2012-01-19T10:38:13Zhttp://eprints.imtlucca.it/id/eprint/1064This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10642012-01-19T10:38:13ZThe evolution of knowledge and the dynamics of an industry network The paper moves a step forward in the direction of establishing a connection between the structure and evolution of knowledge bases and the structure and evolution of organizational forms in innovative activities in a science-intensive industry. The paper has an explicit focus on the dynamics of the network of collaborative agreements in R&D in the pharma/biotech industry after the “molecular biology revolution”. Using a comprehensive dataset, built by the authors integrating several sources in the industry, the dynamics of the network over time is extensively analyzed. With regards to network structure, it is found that, while the size of the network increases over time due to net flows of entry, its topological properties remain relatively unchanged. The evolution of the network has occurred without relevant deformations in the core-periphery profile. With regards to age-dependent propensity to collaborate, the paper finds that the extent of inter-generational collaboration is much more significant than intra-generational collaboration. In addition, the propensity of firms of a given generation to enter into collaboration with firms of a different generation increases with the distance between the two, while the total number of intra-generational collaborations decreases over time and, moreover, tends to decrease for most recent generations. In the paper a unitary and coherent explanation of the evidence is developed, coming to reveal the existence of a striking isomorphism between structural properties of the dynamics of knowledge and of the evolution of network structure. Luigi OrsenigoFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itAndrea BonaccorsiGiuseppe Turchetti2012-01-18T13:19:30Z2012-01-18T13:19:30Zhttp://eprints.imtlucca.it/id/eprint/1063This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10632012-01-18T13:19:30ZL'illusione del controllo nelle politiche pubblicheIt is quite common that public policies take as benchmark mean values of relevant policy variables (average firm size, average productivity, average income, etc.). In such case the policy maker introduces incentives that should change individual behaviour in order to increase average values of the policy relevant variables. When this kind of policies are unsuccessful it is thought that the incentives are badly designed so that the entire problem is considered a problem of "mechanism design". In this paper the Authors maintain that policy makers should always take into account that incentives have an impact not only on individual behaviour but also on the distribution and law of motion of the aggregate phenomena that may be different from the sum of micro behaviours. Three different cases of proportional growth phenomena (firm's size growth, income distribuition and research production) are analyzed, in the paper, through simulations. Some tentative general principles for public policies are identified. Massimo Riccabonimassimo.riccaboni@imtlucca.itSandro TrentoEnrico Zaninotto2012-01-18T11:28:17Z2012-01-18T11:28:17Zhttp://eprints.imtlucca.it/id/eprint/1062This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10622012-01-18T11:28:17ZDoes co-location matter for formal knowledge collaboration in the Swedish biotechnology–pharmaceutical sector?This article addresses the validity of assumptions about the importance of co-locality for innovation, by analyzing whether or not co-location matters for formal knowledge collaboration in the Swedish biotechnology–pharmaceutical sector, or biotech–pharma sector. The population of Swedish biotech–pharma firms has been defined, based on the three criteria of geographical location, their engagement in active knowledge development, and their specialized knowledge/product focus. The firms’ patterns of regional, national and international collaboration with other firms and with universities is analyzed, as well as the differing collaborative patterns of small versus large firm. In addressing the theoretical questions about the relative importance of co-location for innovation, the article also provides an empirical overview of the Swedish biotech–pharma sector, especially trends over time. This paper thus contributes to the literature by expanding our empirical knowledge about one European biotech–pharma sectoral system, e.g. Sweden, as well as addressing the theoretical question about the relative importance of co-location for formal knowledge collaboration.Maureen McKelveyHåkan AlmMassimo Riccabonimassimo.riccaboni@imtlucca.it2012-01-18T11:14:17Z2012-01-18T11:14:17Zhttp://eprints.imtlucca.it/id/eprint/1060This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10602012-01-18T11:14:17ZRadical innovation and network evolutionThis paper examines how a radical technological innovation affects alliance formation of firms and subsequent network structures. We use longitudinal data of interfirm R&D collaborations in the biopharmaceutical industry in which a new technological regime is established. Our findings suggest that it requires radical technological change for firms to leave their embedded path of existing alliances and form new alliances with new partners. While new partners are mostly found through the firms’ existing network, we provide some insight into distant link formation with unknown partners, which contributes to our understanding of how ‘small-worlds’ might emergeSandra PhlippenMassimo Riccabonimassimo.riccaboni@imtlucca.it2012-01-16T09:35:24Z2013-10-10T08:34:21Zhttp://eprints.imtlucca.it/id/eprint/1053This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10532012-01-16T09:35:24ZPersistence and Uncertainty in the Academic CareerRecent shifts in the business structure of universities and a bottleneck in the supply of tenure track positions are two issues that threaten to change the longstanding patronage system in academia. Understanding how institutional changes within academia may affect the overall potential of science requires a better quantitative understanding of how careers evolve over time. Since knowledge spillovers, cumulative advantage, and collaboration are distinctive features of the academic profession, the employment relationship should be designed to account for these factors. We quantify the impact of these factors in the production n_i(t) of a given scientist i by analyzing the longitudinal career data of 300 scientists and compare our results with 21,156 sports careers comprising a non-academic labor force. The increase in the typical size of scientific collaborations has led to the increasingly difficult task of allocating funding and assigning recognition. We use measures of the scientific collaboration radius, which can change dramatically over the course of a career, to provide insight into the role of collaboration in production efficiency. We introduce a model of proportional growth to provide insight into the complex relation between knowledge spillovers, competition, and uncertainty at the individual scale. Our model shows that high competition levels can make careers vulnerable to “sudden death” termination relatively early in the career as a result of negative production fluctuations and not necessarily due to lack of individual persistence.Alexander M. Petersenalexander.petersen@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itH. Eugene StanleyFabio Pammollif.pammolli@imtlucca.it2012-01-16T08:57:08Z2012-06-22T07:36:55Zhttp://eprints.imtlucca.it/id/eprint/1055This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10552012-01-16T08:57:08ZRegolazione di prezzo, innovazione e ciclo di vita dei prodotti: per una riforma del sistema di pricing nel settore farmaceutico tra Stato, industria e cittadiniFabio Pammollif.pammolli@imtlucca.itChiara BonassiMassimo Riccabonimassimo.riccaboni@imtlucca.itNicola C. Salerno2011-12-14T15:19:28Z2011-12-14T15:19:28Zhttp://eprints.imtlucca.it/id/eprint/1042This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10422011-12-14T15:19:28ZManaging technological transitions through R&D alliancesTechnological and market transitions are difficult to manage, and collaborations can be viewed as either resources or constraints in dynamic settings. In the biopharmaceutical industry, a paradigmatic shift in the relevant knowledge bases occurred in the mid-1990s, inducing a structural change in the network of R&D collaborations. Search and relational strategies oriented toward exploration versus exploitation have prevailed in different phases of the network evolution. Therefore, biotechnology firms have experienced overwhelming difficulties in reorienting their learning strategies throughout paradigmatic shifts and ambidextrous organizations have been able to attain superior performances in terms of stability and centralization in the R&D network.Massimo Riccabonimassimo.riccaboni@imtlucca.itRocco Moliterni2011-12-14T15:06:51Z2014-12-04T11:46:29Zhttp://eprints.imtlucca.it/id/eprint/1041This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10412011-12-14T15:06:51ZPareto versus lognormal: a maximum entropy testIt is commonly found that distributions that seem to be lognormal over a broad range change to a power-law (Pareto) distribution for the last few percentiles. The distributions of many physical, natural, and social events (earthquake size, species abundance, income and wealth, as well as file, city, and firm sizes) display this structure. We present a test for the occurrence of power-law tails in statistical distributions based on maximum entropy. This methodology allows one to identify the true data-generating processes even in the case when it is neither lognormal nor Pareto. The maximum entropy approach is then compared with other widely used methods and applied to different levels of aggregation of complex systems. Our results provide support for the theory that distributions with lognormal body and Pareto tail can be generated as mixtures of lognormally distributed units.Marco BeeMassimo Riccabonimassimo.riccaboni@imtlucca.itStefano Schiavo2011-12-13T14:45:12Z2011-12-13T14:45:12Zhttp://eprints.imtlucca.it/id/eprint/1040This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10402011-12-13T14:45:12ZA few special cases: scientific creativity and network dynamics in the field of rare diseasesWe develop a model of scientific creativity and test it in the field of rare diseases. Our model is based on the results of an in-depth case study of the Rett Syndrome. Archival analysis, bibliometric techniques and expert surveys are combined with network analysis to identify the most creative scientists. First, we compare alternative measures of generative and combinatorial creativity. Then, we generalize our results in a stochastic model of socio-semantic network evolution. The model predictions are tested with an extended set of rare diseases. We find that new scientific collaborations among experts in a field enhance combinatorial creativity. Instead, high entry rates of novices are negatively related to generative creativity. By expanding the set of useful concepts, creative scientists gain in centrality. At the same time, by increasing their centrality in the scientific community, scientists can replicate and generalize their results, thus contributing to a scientific paradigm. M. Laura FrigottoMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-09-08T09:58:03Z2011-10-07T08:20:22Zhttp://eprints.imtlucca.it/id/eprint/840This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/8402011-09-08T09:58:03ZThe sustainability of European health care systems: beyond income and agingDuring the last 30 years, health care expenditure (HCE) has been growing much more rapidly than GDP in OECD countries. In this paper, we review the determinants of HCE dynamics in Europe, taking into account the role of income, aging population, technological progress, female labor participation and public budgetary variables.
We show that HCE is a multifaceted phenomenon where
demographic, social, economic, technological and institutional factors all play an important role. The comparison of total, public and private HCE reveals an imbalance of European welfare toward the care of the elderly. European Governments should increasingly rely on pluralistic systems to balance sustainability and access and equilibrate the distribution of resources across the functions of the public welfare system.Fabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itLaura Magazzini2011-09-07T12:58:03Z2014-01-24T14:19:09Zhttp://eprints.imtlucca.it/id/eprint/825This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/8252011-09-07T12:58:03ZInnovation and corporate dynamics: a theoretical frameworkWe provide a detailed analysis of a generalized proportional growth model (GPGM) of innovation and corporate dynamics that encompasses the Gibrat’s Law of Proportionate Effect and the Simon growth process as particular instances. The predictions of the model are derived in terms of (i) firm size distribution, (ii) the distribution of firm growth rates, and (iii-iv) the relationships between firm size and the mean and variance of firm growth rates. We test the model against data from the worldwide pharmaceutical industry and find its predictions to be in good agreement with empirical evidence on all four dimensions.Jakub GrowiecFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-07-05T10:55:07Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/702This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/7022011-07-05T10:55:07ZInnovation and competitiveness in European biotechnologyFabio Pammollif.pammolli@imtlucca.itA. AllansdottirAndrea BonaccorsiAlfonso GambardellaM. MarianiLuigi OrsenigoMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-07-05T10:39:26Z2014-01-24T14:28:18Zhttp://eprints.imtlucca.it/id/eprint/701This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/7012011-07-05T10:39:26ZMedical devices competitiveness and impact on public health expenditureFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itClaudia OglialoroLaura MagazziniGianluca BaioNicola C. Salerno2011-07-01T14:44:57Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/690This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6902011-07-01T14:44:57ZIl settore farmaceutico tra barriere alla concorrenza e regolazione sul lato del consumoFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itNicola C. Salerno2011-07-01T13:08:51Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/688This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6882011-07-01T13:08:51ZOn firm growth in networks This paper is explorative in nature. Based on an empirical analysis of two different industrial settings (life sciences, LS; information and communication technologies, ICT), it investigates network growth and firm growth in networks. We find a remarkable correspondence between a few fundamental findings of the `old' stochastic approach to the analysis of firm internal growth, and empirically observed patterns of firm external growth through collaborative agreements. We show that scale-free behavior in real-world industrial networks can be accounted for by a general and parsimonious model, originally developed by Herbert Simon in 1955, based on entry and proportional growth. However, relevant departures from the stochastic benchmark are revealed that cannot be ascribed to the effect of mergers and acquisitions (M&As) and growth autocorrelation. Moreover, different regimes of growth are found to be at work in the life sciences for originators versus developers of new business opportunities, reflecting the fact that growth is driven by specialization and division of labor in the processes of generation and attraction/development of technological opportunities.Fabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-07-01T10:40:04Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/687This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6872011-07-01T10:40:04ZOn size and growth of business firms We study size and growth distributions of products and business firms in the context of a given industry. Firm size growth is analyzed in terms of two basic mechanisms, i.e., the increase of the number of new elementary business units and their size growth. We find a power-law relationship between size and the variance of growth rates for both firms and products, with an exponent between -0.17 and -0.15, with a remarkable stability upon aggregation. We then introduce a simple and general model of proportional growth for both the number of firm independent constituent units and their size, which conveys a good representation of the empirical evidences. This general and plausible generative process can account for the observed scaling in a wide variety of economic and industrial systems. Our findings contribute to shed light on the mechanisms that sustain economic growth in terms of the relationships between the size of economic entities and the number and size distribution of their elementary components.Fabio Pammollif.pammolli@imtlucca.itG. De FabritiisMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-07-01T10:02:40Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/686This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6862011-07-01T10:02:40ZMarket Structure And Drug Innovation An explosion of knowledge and a growing array of tools and technologies have transformed modern drug R&D, while its cost has risen by a sizable amount. At the same time, the unchecked increase in health care and prescription drug spending has spawned cost containment policies that are restricting the demand for drugs in all major markets. This Perspective explores the interplay between technological advances and regulatory policies and their likely impact on the dynamics of the pharmaceutical industry. Fabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-07-01T09:32:26Z2013-10-10T08:38:12Zhttp://eprints.imtlucca.it/id/eprint/685This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6852011-07-01T09:32:26ZThe growth of business firms: Theoretical framework and empirical evidenceWe introduce a model of proportional growth to explain the distribution Pg(g) of business-firm growth rates. The model predicts that Pg(g) is exponential in the central part and depicts an asymptotic power-law behavior in the tails with an exponent ζ = 3. Because of data limitations, previous studies in this field have been focusing exclusively on the Laplace shape of the body of the distribution. In this article, we test the model at different levels of aggregation in the economy, from products to firms to countries, and we find that the predictions of the model agree with empirical growth distributions and size-variance relationships.Fabio Pammollif.pammolli@imtlucca.itDongfeng FuSergey V. BuldyrevMassimo Riccabonimassimo.riccaboni@imtlucca.itKaushik MatiaKazuko YamasakiH. Eugene Stanley2011-07-01T08:58:09Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/683This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6832011-07-01T08:58:09ZPreferential attachment and growth dynamics in complex systemsComplex systems can be characterized by classes of equivalency of their elements defined according to system specific rules. We propose a generalized preferential attachment model to describe the class size distribution. The model postulates preferential growth of the existing classes and the steady influx of new classes. According to the model, the distribution changes from a pure exponential form for zero influx of new classes to a power law with an exponential cut-off form when the influx of new classes is substantial. Predictions of the model are tested through the analysis of a unique industrial database, which covers both elementary units (products) and classes (markets, firms) in a given industry (pharmaceuticals), covering the entire size distribution. The model’s predictions are in good agreement with the data. The paper sheds light on the emergence of the exponent τ≈2 observed as a universal feature of many biological, social and economic problems.Fabio Pammollif.pammolli@imtlucca.itKazuko YamasakiKaushik MatiaSergey V. BuldyrevDongfeng FuMassimo Riccabonimassimo.riccaboni@imtlucca.itH. Eugene Stanley2011-06-30T14:28:11Z2011-10-07T08:27:21Zhttp://eprints.imtlucca.it/id/eprint/629This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6292011-06-30T14:28:11ZTechnological change and network dynamics: Lessons from the pharmaceutical industryIn this paper, we investigate how underlying relevant technological conditions induce distinguishable patterns of change in industry structure and evolution. A mapping is detected between the specific nature of problem decompositions and research techniques at the micro level of knowledge bases, and patterns of structural evolution at the macro level of the industry network. The graph-theoretic techniques we introduce map major technological discontinuities on changes observed at the level of dominant organization forms. They might have applications in other domains, whenever the identification of structural breaks and homological relationships between technological and industrial spaces are important issues.Fabio Pammollif.pammolli@imtlucca.itLuigi OrsenigoMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:28:02Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/630This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6302011-06-30T14:28:02ZA Comparison of U. S. and European University-Industry Relations in the Life SciencesWe draw on diverse data sets to compare the institutional organization of upstream life science research across the United States and Europe. Understanding cross-national differences in the organization of innovative labor in the life sciences requires attention to the structure and evolution of biomedical networks involving public research organizations (universities, government laboratories, nonprofit research institutes, and research hospitals), science-based biotechnology firms, and multinational pharmaceutical corporations. We use network visualization methods and correspondence analyses to demonstrate that innovative research in biomedicine has its origins in regional clusters in the United States and in European nations. But the scientific and organizational composition of these regions varies in consequential ways. In the United States, public research organizations and small firms conduct R&D across multiple therapeutic areas and stages of the development process. Ties within and across these regions link small firms and diverse public institutions, contributing to the development of a robust national network. In contrast, the European story is one of regional specialization with a less diverse group of public research organizations working in a smaller number of therapeutic areas. European institutes develop local connections to small firms working on similar scientific problems, while cross-national linkages of European regional clusters typically involve large pharmaceutical corporations. We show that the roles of large and small firms differ in the United States and Europe, arguing that the greater heterogeneity of the U. S. system is based on much closer integration of basic science and clinical development.Fabio Pammollif.pammolli@imtlucca.itJason Owen-SmithMassimo Riccabonimassimo.riccaboni@imtlucca.itWalter W. Powell2011-06-30T14:27:56Z2011-08-31T14:40:38Zhttp://eprints.imtlucca.it/id/eprint/632This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6322011-06-30T14:27:56ZThe productivity crisis in pharmaceutical R&DAdvances in the understanding of the molecular basis of diseases have expanded the number of plausible therapeutic targets for the development of innovative agents in recent decades. However, although investment in pharmaceutical research and development (R&D) has increased substantially in this time, the lack of a corresponding increase in the output in terms of new drugs being approved indicates that therapeutic innovation has become more challenging. Here, using a large database that contains information on R&D projects for more than 28,000 compounds investigated since 1990, we examine the decline of R&D productivity in pharmaceuticals in the past two decades and its determinants. We show that this decline is associated with an increasing concentration of R&D investments in areas in which the risk of failure is high, which correspond to unmet therapeutic needs and unexploited biological mechanisms. We also investigate the potential variations in productivity with regard to the regional location of companies and find that although companies based in the United States and Europe differ in the composition of their R&D portfolios, there is no evidence of any productivity gap.Fabio Pammollif.pammolli@imtlucca.itLaura MagazziniMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:27:43Z2014-12-18T15:28:35Zhttp://eprints.imtlucca.it/id/eprint/634This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6342011-06-30T14:27:43ZScale-free models for the structure of business firm networksWe study firm collaborations in the life sciences and the information and communication technology sectors. We propose an approach to characterize industrial leadership using k-shell decomposition, with top-ranking firms in terms of market value in higher k-shell layers. We find that the life sciences industry network consists of three distinct components: a “nucleus,” which is a small well-connected subgraph, “tendrils,” which are small subgraphs consisting of small degree nodes connected exclusively to the nucleus, and a “bulk body,” which consists of the majority of nodes. Industrial leaders, i.e., the largest companies in terms of market value, are in the highest k-shells of both networks. The nucleus of the life sciences sector is very stable: once a firm enters the nucleus, it is likely to stay there for a long time. At the same time we do not observe the above three components in the information and communication technology sector. We also conduct a systematic study of these three components in random scale-free networks. Our results suggest that the sizes of the nucleus and the tendrils in scale-free networks decrease as the exponent of the power-law degree distribution λ increases, and disappear for λ≥3. We compare the k-shell structure of random scale-free model networks with two real-world business firm networks in the life sciences and in the information and communication technology sectors. We argue that the observed behavior of the k-shell structure in the two industries is consistent with the coexistence of both preferential and random agreements in the evolution of industrial networks.Maksim KitsakMassimo Riccabonimassimo.riccaboni@imtlucca.itShlomo HavlinFabio Pammollif.pammolli@imtlucca.itH. Eugene Stanley2011-06-30T14:27:33Z2011-08-31T14:40:38Zhttp://eprints.imtlucca.it/id/eprint/635This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6352011-06-30T14:27:33ZPatent disclosure and R&D competition in pharmaceuticalsThe prominent role played by patents within the pharmaceutical domain is unquestionable. In this paper, we focus on a relatively neglected implication of patents: the effect of patent-induced information disclosure on the dynamics of R&D and market competition. The study builds upon the combination of two large datasets, linking the information about patents to firm-level data on R&D projects and their outcome. Two case studies in the fields of anti-inflammatory compounds and cancer research complement our analysis. We argue that patent disclosure induces R&D competition and shapes firms' technological trajectories. In fact, we show that under conditions of uncertainty, patent disclosure can contribute to generate knowledge spillovers, promoting multiple parallel research efforts on plausible targets and stimulating private investment and competition. Fabio Pammollif.pammolli@imtlucca.itLaura MagazziniMassimo Riccabonimassimo.riccaboni@imtlucca.itMaria Alessandra Rossi2011-06-30T14:27:17Z2013-10-10T08:37:45Zhttp://eprints.imtlucca.it/id/eprint/637This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6372011-06-30T14:27:17ZThe size variance relationship of business firm growth ratesThe relationship between the size and the variance of firm growth rates is known to follow an approximate power-law behavior σ(S) ≈ S−β(S) where S is the firm size and β(S) ≈ 0.2 is an exponent that weakly depends on S. Here, we show how a model of proportional growth, which treats firms as classes composed of various numbers of units of variable size, can explain this size-variance dependence. In general, the model predicts that β(S) must exhibit a crossover from β(0) = 0 to β(∞) = 1/2. For a realistic set of parameters, β(S) is approximately constant and can vary from 0.14 to 0.2 depending on the average number of units in the firm. We test the model with a unique industry-specific database in which firm sales are given in terms of the sum of the sales of all their products. We find that the model is consistent with the empirically observed size-variance relationship. Fabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itSergey V. BuldyrevLinda PontaH. Eugene Stanley2011-06-30T14:27:10Z2011-08-31T14:40:38Zhttp://eprints.imtlucca.it/id/eprint/638This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6382011-06-30T14:27:10ZOn the size distribution of business firms The size distribution of business firms is explained using number and size of firms' constituent components. It is a lognormal distribution multiplied by a stretching factor which can lead to a Pareto upper tail. This result is confirmed empirically.Fabio Pammollif.pammolli@imtlucca.itJakub GrowiecMassimo Riccabonimassimo.riccaboni@imtlucca.itH. Eugene Stanley2011-06-30T14:27:04Z2011-08-31T14:40:38Zhttp://eprints.imtlucca.it/id/eprint/639This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6392011-06-30T14:27:04ZThe Growth of Business Firms: Facts and TheoryWe refer to the framework developed by Ijiri and Simon (1977) and to the notion of independent submarkets (Sutton 1998) to provide a simple candidate explanation for the shape of the firm growth distribution based on a model of proportional growth at the level of both the introduction of new products by firms and their size dynamics. We exploit the features of a unique longitudinal data set which covers the entire distribution of products and firms in the worldwide pharmaceutical industry to test the model at different levels of aggregation as well as at different time lags. Econometric investigations show that the model's predictions are in good agreement with empirical evidence. (JEL: L11, L65)Fabio Pammollif.pammolli@imtlucca.itSergey V. BuldyrevJakub GrowiecMassimo Riccabonimassimo.riccaboni@imtlucca.itH. Eugene Stanley2011-06-30T14:26:56Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/640This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6402011-06-30T14:26:56ZEconomic evaluation of HIV treatments: The I.CO.N.A. cohort studyObjective: To describe the changes in costs of care for HIV-positive patients in Italy after the spread of antiretroviral combination therapies (HAART).Methods: Five thousand four hundred and twenty-two patients from the I.CO.N.A. (Italian Cohort Naive Antiretrovirals) study were followed between 1997 and 2002. Costs included antiretroviral therapies (ART), hospital admissions, prophylaxis, and main laboratory examinations. The perspective was that of the National Health Service.Results: Admission costs per person-year decreased from 2148 euro in 1997 to 256 in 2002, while the average annual costs of ART increased from 2145 to 3149 euro (1997 prices). From 1997 to1999, ART costs increased from 42.3 to 85.9 of the total, while admission costs decreased from 42.3 to 7.0 and prophylaxis from 7.3 to 1.7. The breakdown of ART costs shows how dual therapies decreased over time in favor of HAART, falling from 26.8 in 1997 to 5.9 in 2002. Patients with fewer than five treatment switches had the lowest costs distributions over the entire observation period.Conclusions: From 1997 to 2002 inpatient costs progressively decreased in favor of antiretroviral therapy. Annual average costs per patient decreased, while total direct costs increased over time: health resources, initially concentrated on hospitalized patients were then distributed over a growing number of subjects.Fabio Pammollif.pammolli@imtlucca.itMonica MeritoAndrea BonaccorsiMassimo Riccabonimassimo.riccaboni@imtlucca.itGianluca BaioClaudio AriciAntonella D'Arminio MonfortePatrizio PezzottiDario CorsiniAndrea TramarinRoberto CaudaVincenzo ColangeliGiuseppe Pastore2011-06-30T14:26:40Z2014-12-18T15:44:51Zhttp://eprints.imtlucca.it/id/eprint/643This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6432011-06-30T14:26:40ZBetweenness centrality of fractal and nonfractal scale-free model networks and tests on real networksWe study the betweenness centrality of fractal and nonfractal scale-free network models as well as real networks. We show that the correlation between degree and betweenness centrality C of nodes is much weaker in fractal network models compared to nonfractal models. We also show that nodes of both fractal and nonfractal scale-free networks have power-law betweenness centrality distribution P(C)∼C−δ. We find that for nonfractal scale-free networks δ=2, and for fractal scale-free networks δ=2−1∕dB, where dB is the dimension of the fractal network. We support these results by explicit calculations on four real networks: pharmaceutical firms (N=6776), yeast (N=1458), WWW (N=2526), and a sample of Internet network at the autonomous system level (N=20566), where N is the number of nodes in the largest connected component of a network. We also study the crossover phenomenon from fractal to nonfractal networks upon adding random edges to a fractal network. We show that the crossover length ℓ*, separating fractal and nonfractal regimes, scales with dimension dB of the network as p−1∕dB, where p is the density of random edges added to the network. We find that the correlation between degree and betweenness centrality increases with p.Maksim KitsakShlomo HavlinGerald PaulMassimo Riccabonimassimo.riccaboni@imtlucca.itFabio Pammollif.pammolli@imtlucca.itH. Eugene Stanley2011-06-30T14:26:33Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/644This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6442011-06-30T14:26:33ZInnovation and industrial leadership: lessons from pharmaceuticalsFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:26:24Z2011-08-31T14:40:38Zhttp://eprints.imtlucca.it/id/eprint/645This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6452011-06-30T14:26:24ZHealth Services in an Open Transatlantic Market: A European PerspectiveFabio Pammollif.pammolli@imtlucca.itChiara BonassiMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:26:16Z2013-11-21T13:03:15Zhttp://eprints.imtlucca.it/id/eprint/646This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6462011-06-30T14:26:16ZA generalized preferential attachment model for business firms growth rates: II. Mathematical treatmentWe present a preferential attachment growth model to obtain the distribution P(K) of number of units K in the classes which may represent business firms or other socio-economic entities. We found that P(K) is described in its central part by a power law with an exponent ϕ = 2+b/(1-b) which depends on the probability of entry of new classes, b. In a particular problem of city population this distribution is equivalent to the well known Zipf law. In the absence of the new classes entry, the distribution P(K) is exponential. Using analytical form of P(K) and assuming proportional growth for units, we derive P(g), the distribution of business firm growth rates. The model predicts that P(g) has a Laplacian cusp in the central part and asymptotic power-law tails with an exponent ζ = 3. We test the analytical expressions derived using heuristic arguments by simulations. The model might also explain the size-variance relationship of the firm growth rates. Fabio Pammollif.pammolli@imtlucca.itSergey V. BuldyrevMassimo Riccabonimassimo.riccaboni@imtlucca.itKazuko YamasakiDongfeng FuKaushik MatiaH. Eugene Stanley2011-06-30T14:26:09Z2013-11-21T13:05:56Zhttp://eprints.imtlucca.it/id/eprint/647This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6472011-06-30T14:26:09ZA generalized preferential attachment model for business firms growth rates: I. Empirical evidenceWe introduce a model of proportional growth to explain the distribution P(g) of business firm growth rates. The model predicts that P(g) is Laplace in the central part and depicts an asymptotic power-law behavior in the tails with an exponent ζ = 3. Because of data limitations, previous studies in this field have been focusing exclusively on the Laplace shape of the body of the distribution. We test the model at different levels of aggregation in the economy, from products, to firms, to countries, and we find that the predictions are in good agreement with empirical evidence on both growth distributions and size-variance relationships. Fabio Pammollif.pammolli@imtlucca.itDongfeng FuSergey V. BuldyrevMassimo Riccabonimassimo.riccaboni@imtlucca.itKaushik MatiaKazuko YamasakiH. Eugene Stanley2011-06-30T14:25:58Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/649This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6492011-06-30T14:25:58ZInnovation and corporate growth in the evolution of the drug industryThis work studies the processes of growth of the worlds top 150 pharmaceutical firms, on the grounds of an original database which also allows disaggregate analysis at the level of single therapeutical classes and chemical entities. Our findings show that the industry -- whose long-term evolution is driven by innovation, imitation and permanent creation of new markets -- displays (i) "fat tails" in the distribution of growth shocks, present at all levels of aggregation, with (relatively rare) big "spurs of growth", (ii) a significant autocorrelation of growth rates, (iii) a fall of variance of growth rates with size entirely dependent on corporate diversification patterns, in turn plausibly shaped by the "competence scope" of each firm, and (iv) different "lifecycles" of diverse types of products, and persistent forms of heterogeneity across firms in terms of innovative output, which, however, do not not seem to affect comparative growth performances.Fabio Pammollif.pammolli@imtlucca.itGiulio BottazziGiovanni DosiMarco LippiMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:25:51Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/650This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6502011-06-30T14:25:51ZStatistical properties of business firms structure and growthWe analyze a database comprising quarterly sales of 55624 pharmaceutical products commercialized by 3939 pharmaceutical firms in the period 1992-2001. We study the probability density function (PDF) of growth in firms and product sales and find that the width of the PDF of growth decays with the sales as a power law with exponent β = 0.20 ± 0.01. We also find that the average sales of products scales with the firm sales as a power law with exponent α = 0.57 ± 0.02. And that the average number products of a firm scales with the firm sales as a power law with exponent γ = 0.42 ± 0.02. We compare these findings with the predictions of models proposed till date on growth of business firms.Fabio Pammollif.pammolli@imtlucca.itKaushik MatiaDongfeng FuSergey V. BuldyrevMassimo Riccabonimassimo.riccaboni@imtlucca.itH. Eugene Stanley2011-06-30T14:25:42Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/651This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6512011-06-30T14:25:42ZDynamic competition in pharmaceuticals:
Patent expiry, generic penetration, and industry structureThis paper investigates patterns of industrial dynamics and competition in the pharmaceutical industry, with particular reference to the consequences of patent expiry in different countries. We focus on the competition at the level of single chemical entities, distinguishing between original brands and generic products. Quarterly data, spanning from July 1987 to December 1998, on sales of pharmaceutical products in four countries (USA, UK, Germany, and France) constitute the basis of our analysis. All the products containing major molecules whose patent expiration date lies between 1986 and 1996 are included in our sample. We show how diffusion of generics is linked to the characteristics of the market and investigate how price dynamics of original products are affected by generic competition. Our empirical investigation shows that the dynamics of drug prices and the competition by generic drugs vary significantly across countries. This heterogeneity notwithstanding, a clear distinction seems to emerge. On the one hand, systems that rely on market-based competition in pharmaceuticals promote a clear distinction between firms that act as innovators and firms that act as imitators after patent expiry. Here, original products enjoy premium prices and exclusivity profits under patent protection, and face fierce price competition after patent expiry. On the other hand, in systems that rely on administered prices, penetration by generic drugs tends to be rather limited. Its descriptive and preliminary nature notwithstanding, our analysis seems to have relevant implications at different levels of generality, especially for Europe.Fabio Pammollif.pammolli@imtlucca.itLaura MagazziniMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:25:35Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/652This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6522011-06-30T14:25:35ZTechnological Competencies in Networks of InnovatorsFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:25:27Z2014-07-02T10:38:17Zhttp://eprints.imtlucca.it/id/eprint/654This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6542011-06-30T14:25:27ZThe nature and extent of the market for technology in biopharmaceuticalsThe biopharmaceutical industry is a typical example of the development of technological collaborations, as well as of technological competition, between larger established firms and smaller high-tech specialist firms (the so-called New Biotechnology Firms — NBFs). These two types of firms perform innovative activities at different stages, with different degree of risk, and with different probability of failure. By using a comprehensive database of 2078 drug R&D projects promoted all over the world during the 1990s, this study assesses the different performance of R&D processes conducted under different governance structures, most notably projects that are fully internalised by the companies vis-àvis projects developed in collaboration with other firms. Moreover, this study compares the different specialisation and performance of large drug companies with respect to the NBFs. Results show that the established pharmaceutical companies have comparative advantages with respect to NBFs in drug development, while there is no advantage related to scale in drug discovery. Furthermore, NBFs undertake less risky project, which are more likely to fail at earlier clinical stages.Ashish AroraAlfonso GambardellaFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:25:20Z2011-08-31T14:40:40Zhttp://eprints.imtlucca.it/id/eprint/656This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6562011-06-30T14:25:20ZVariety and Irreversibility in Scientific and Technological Systems: the Evolution of an Industry NetworkFabio Pammollif.pammolli@imtlucca.itLuigi OrsenigoMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:25:13Z2014-07-01T08:32:54Zhttp://eprints.imtlucca.it/id/eprint/658This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6582011-06-30T14:25:13ZPatent value and R&D competitionThis paper aims at characterizing the dynamics of R&D competition within the pharmaceutical domain, focusing on the role of patent disclosure, the extent of uncertainty, and role of scientific advances. Following the empirical literature in the economics of innovation, we employ patents as a proxy for innovations and patent citations as a measure of knowledge utilization and spillovers. Pharmaceuticals are a unique setting in this respect, given the characteristics of the innovation process, that make patents an important means for appropriating returns from R&D. All in all, the analysis provides evidence that in the pharmaceutical industry research advances through a process of trial-and-error, where both successes and failures set the ground for subsequent innovations. The disclosure of the information about new compounds or new mechanisms of action play an important role in this industry fostering R&D efforts and competition in identified therapeutic markets in the search for new marketable products building both on failures and successes. The outcome of this process is highly uncertain and building on a success provides no certainty about the outcome of the search. Indeed, discontinued patents building on previous failures exhibit a higher citation rate. We also contribute to the debate about the relevance of citation in measuring patent value by looking at the relationship between patent citations and product sales.Fabio Pammollif.pammolli@imtlucca.itLaura MagazziniMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:24:45Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/662This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6622011-06-30T14:24:45ZTechnological Paradigms and the Evolution of Networks: Lessons from the Pharmaceutical IndustryFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:24:33Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/663This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6632011-06-30T14:24:33ZPublic Research and Industrial Innovation: A comparison of U.S. and European Innovation Systems in the Life SciencesFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itWalter W. PowellJason Owen-Smith2011-06-30T14:24:24Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/664This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6642011-06-30T14:24:24ZTechnological regimes and the evolution of networks of innovators. Lessons from biotechnology and pharmaceuticalsIn this paper, we analyse the relationships between technological regimes, regimes of local interaction, and the global structure of an industrial network. Given the complexity of the task, we follow a semi-inductivist approach, combining quantitative empirical analyses and simulative exercises. We show that the topological properties of the R&D network in pharmaceuticals are the result of neither a purely random nor of a cumulative process of growth. Instead, they emerge from a mixture of the two generative processes, under a regime of intense and stable entry. This paper should be considered only as a first step towards the understanding of some general determinants of industry networks growth. Despite its limitations, it provides a parsimonious and general framework to reverse engineer the growth of networks in different industries. Some of the current limitations of our analysis could be overcome, in the future, based on a higher availability of data on real systems and, in particular, of detailed topological and economic information on real-world networks. While currently such data are rare, the increasing interest in industrial networks should soon lead to the development of suitable data sets, offering further guidance for modelling and interpreting the growth of these complex and important economic systems. Fabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:24:14Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/665This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6652011-06-30T14:24:14ZThe Nature and the Extent of Markets for TechnologyFabio Pammollif.pammolli@imtlucca.itAshish AroraAlfonso GambardellaMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:24:03Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/666This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6662011-06-30T14:24:03ZEurope and the United States: The Power of Networks. Lessons from Technology TransferFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itJason Owen-SmithWalter W. Powell2011-06-30T14:23:48Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/668This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6682011-06-30T14:23:48ZTechnological Regimes and the Growth of Networks: An Empirical AnalysisThis paper shows how specific technological
and relational regimes have shaped the growth of the network
of R&D collaborative agreements in pharmaceuticals in the
1990s. Our analysis reveals the existence of a complex set of
regimes of firm growth within the network, providing additional
evidence supporting prediction that both growth and
innovative activities of large and small firms respond, even
within a given industry, to considerably different technological
and economic factors. Moreover, the paper shows, in the
context of a specific industry and by means of a series of
preliminary and explorative empirical analyses, that information
on the topological properties of a given industrial settings
and on roles/positions of organizations within it can be used
to disentangle some fundamental generative processes underlying
observed processes of growth. This result contributes
to the “old” stochastic approach to firm growth, in the
direction of building parsimonious and, at the same time, more
realistic, representations of processes of industrial growth.Fabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:22:23Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/679This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6792011-06-30T14:22:23ZSicurezza, innovazione, crescitaFabio Pammollif.pammolli@imtlucca.itAndrea PaciMassimo Riccabonimassimo.riccaboni@imtlucca.it