In my first K99-R00 publication analysis post, I presented the distribution of the number of publications for the FY2007 K99-R00 cohort. In this post, I examine the distributions of the numbers of authors per paper.
For 134 K99 investigators for which I have been able to identify publications relatively unambiguously through PubMed and who transitioned to a R00 award, a histogram of the number of authors per publication is shown below:
The median number of authors is 5 and the mean is 6.5. Of course, average number of authors per publication varies from investigator, reflecting different circumstances, areas of science, and other factors. The distribution is shown below:
How does the average number of authors per publication relate to the number of publications?
As this plot shows, these two parameters are correlated with a correlation coefficient of 0.47. Investigators with a larger number of publications tend to have more authors per publication.
One way to correct for the influence of an increased number of authors on the number of publications is to weight each publication by 1/(number of authors) (as was suggested by a comment on Twitter). In this scenario, a paper with two authors would be worth 1/2 while a paper with 10 authors would be worth 1/10.
This weighted sum of publication is plotted versus the total number of publications below:
This tightens the distribution substantially and the correlation coefficient increases to 0.83. One interpretation of this is that differences in authorship practices do influence the number of publication for a substantial part of the distribution. The investigators on the tail of the distribution with a large number of publications still lie on the edge of the distribution with this correction. In general, these investigators have been successful in obtaining substantial resources subsequent to their R00 awards, leading to an increased number of publications.