%0 Journal Article
%A Petersen, Alexander M.
%A Succi, Sauro
%D 2013
%F eprints:2376
%I Elsevier
%J Journal of Informetrics
%K Science of science; Citation impact; Rank stability; h-Index
%N 4
%P 823-832
%T The Z-index: A geometric representation of productivity and impact which accounts for information in the entire rank-citation profile
%U http://eprints.imtlucca.it/2376/
%V 7
%X We present a simple  generalization of Hirsch's h-index, Z \equiv \sqrt{h^{2}+C}/\sqrt 5, where C is the total number of citations. Z is aimed at correcting  the potentially excessive penalty made by h on a scientist's highly cited papers, because for the majority of scientists analyzed, we find the excess citation fraction (C-h^{2})/C  to be distributed closely around the value 0.75, meaning that 75 percent of the author's impact is neglected. Additionally, Z is less sensitive to local changes in a scientist's citation profile, namely perturbations  which increase h while only marginally affecting C. Using real career data for 476 physicists careers and 488 biologist careers, we analyze both the distribution of Z and the rank stability of Z with respect to the Hirsch index h and the Egghe index g. We analyze careers distributed across a wide range of total impact, including top-cited physicists and biologists for benchmark comparison. In practice, the Z-index requires the same information needed to calculate h and could be effortlessly  incorporated within career profile   databases, such as Google Scholar and ResearcherID. Because Z incorporates information from the entire publication profile while being more robust than h and g to local perturbations, we argue that Z is better suited for ranking comparisons in academic  decision-making scenarios comprising a large number of scientists.