Spurred, in part, by Drugmonkey's post, I have been thinking further about the analysis I did relating the number of publications to the number of authors per publication. I realize that I did not fully grasp the implications of my results. A key question is whether an increased number of publications per investigator can be accounted for by an increased number of authors per publication.
Two limiting cases can be considered. In the first case, the average number of authors per publication would be essentially constant, regardless of the number of publications by a given investigator. This case is ruled out by the data presented that show that the average number of authors is positively correlated with the number of publications with a correlation coefficient of 0.47.
In the second case, the average number of authors per publication increases directly with the number with the number of publications. In this case, the plot of the number of publications weighted by 1/the number of authors versus the number of publications (the plot highlighted by Drugmonkey) would be a line with slope 0. However, the trend line in the plot has a substantial positive slope. Previously, I focused on the fact that the correlation coefficient for this plot is large (0.83). However, this is not really the point. It is not surprising that the weighted number of publications is relatively well correlated with the number of publications. It is the slope of the line that conveys the information.
Simulations suggest that the slope line in this plot is close to what one would expect if the number of authors per publication were constant. Another way to see the same point is to consider the average number of authors for investigators with the smallest and largest number of publications.
20 investigators with the fewest publications: Average number of publications-9.1, Average number of authors per publication-4.6
20 investigators with the most publications: Average number of publications-57.4-Average number of authors per publication-7.3
Thus, while the number of publications increases by a factor of 57.4/9.1 = 6.3, the average number of authors per publication increased by a factor of 7.5/4.6 = 1.6.
These data do not support the notion that the increased number of publications is due primarily to an increased number of authors per publication.
As I posted subsequently, a major factor contributing to the number of publication is the amount of support that each investigator has been able to garner.