On the time dependence of the h-index

The time dependence of the h-index is analyzed by considering the average behavior of h as a function of the academic age AA for about 1400 Italian physicists, with career lengths spanning from 3 to 46 years. The individual h-index is strongly correlated with the square root of the total citations Nc: h approximate to 0.53 NC. For academic ages ranging from 12 to 24 years, the distribution of the time scaled index h/ sic AA is approximately time-independent and it is well described by the Gompertz function. The time scaled index h/ sic AA has an average approximately equal to 3.8 and a standard deviation approximately equal to 1.6. Finally, the time scaled index h/ sic AA appears to be strongly correlated with the contemporary h-index hc. (C) 2012 Elsevier Ltd. All rights reserved.