TY  - JOUR
VL  - 81
N1  - © 2010 American Physical Society
ID  - eprints634
A1  - Kitsak, Maksim
A1  - Riccaboni, Massimo
A1  - Havlin, Shlomo
A1  - Pammolli, Fabio
A1  - Stanley, H. Eugene
PB  - American Physical Society
SN  - 1539-3755
N2  - We 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 ? increases, and disappear for ??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.
AV  - public
TI  - Scale-free models for the structure of business firm networks
KW  - PACS number(s): 89.75.Hc
Y1  - 2010/03//
UR  - http://link.aps.org/doi/10.1103/PhysRevE.81.036117
IS  - 3
JF  - Physical Review E
ER  -