Research groups: how big should they be?
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Abstract
We have investigated the relationship between research group size and productivity in the life sciences in the United Kingdom using data from 398 principle investigators (PIs). We show that the number of publications increases linearly with group size, but that the slope is modest relative to the intercept, and that the relationship explains little of the variance in productivity. A comparison of the slope and intercept suggests that PIs contribute on average 5-times more productivity than an average group member and using multiple regression we estimate that post-doctoral researchers are approximately 3–times more productive than PhD students. We also find that the impact factor and the number of citations are both non-linearly related to group size such that there is a maximum. However, the relationships explain little of the variance and the curvatures are shallow so the impact factor and the number of citations do not greatly depend upon group size. The intercept is large relative to curvature suggesting that the PI is largely responsible for the impact factor and the number of citations from their group. Surprisingly we find this non-linear relationship for post-docs, but for PhD students we observe a slight but significant decrease in the impact factor. The results have important implications for the funding of research. Given a set number of Pis there is no evidence of diminishing returns in terms of the number of papers published and only a very weak cost to very large groups in terms of where those papers are published and the number of citations they receive. However, the results do suggest that it might be more productive to invest in new permanent members of faculty rather than additional post-docs and PhD students.
Cite this as
2015. Research groups: how big should they be? PeerJ PrePrints 3:e812v1 https://doi.org/10.7287/peerj.preprints.812v1note This preprint is not peer-reviewed. You may wish to reference the subsequent peer-reviewed version of this article.
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This is a submission to PeerJ for review.
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Supplemental Information
Supplementary Table S1
The anonymised data used in the analysis
Additional Information
Competing Interests
The authors declare they have no competing interests.
Author Contributions
Isabelle Cook performed the experiments, analyzed the data, contributed reagents/materials/analysis tools.
Sam Grange performed the experiments, analyzed the data, contributed reagents/materials/analysis tools.
Adam Eyre-Walker conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Human Ethics
The following information was supplied relating to ethical approvals (i.e., approving body and any reference numbers):
It was not considered necessary to submit this study for ethical review given the nature of the project – simply requesting research group size information directly from PIs. All participants gave their written consent in the form of an email reply.
Funding
The authors declare there was no funding for this work.
