Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

H-index: age and sex make it unreliable

Sir

The h-index seems to be breaking away from the bibliometric pack, in the race to become a favoured measure of scientific performance ('Achievement index climbs the ranks' Nature 448, 737; 2007). However, if the h-index is to become an assessment tool commonly used by university administrators and government bureaucrats, those using it should be aware of its pitfalls.

As noted in your News story, tallying how many papers a researcher publishes (their productivity) gives undue merit to those who publish many inconsequential papers. But at least for ecologists and evolutionary biologists, the h-index is highly correlated with productivity (r = 0.77; see C. D. Kelly and M. D. Jennions Trends Ecol. Evol. 21, 167–170; 2006).

This is worrisome, because the h-index is easily misconstrued as an equitable measure of research quality. We offer two examples.

First, female ecologists and evolutionary biologists publish fewer papers than their male counterparts, and they have significantly lower h-indices. Should administrators therefore conclude that men are better researchers? No. The gender difference vanishes if we control for productivity. It seems unlikely that this phenomenon is restricted to ecology and evolution.

Second, the h-index increases with age and using the ratio of the two can be problematic. Therefore, reliably comparing the performance of younger researchers with older ones is difficult.

Author information

Affiliations

Authors

Additional information

Contributions to Correspondence may be submitted to correspondence@nature.com. They should be no longer than 300 words. Published contributions are edited. We welcome comments at Nautilus ( http://blogs.nature.com/nautilus ).

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Kelly, C., Jennions, M. H-index: age and sex make it unreliable. Nature 449, 403 (2007). https://doi.org/10.1038/449403c

Download citation

Further reading

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing