At the journal Molecular Ecology, we find little evidence for the common belief that the peer-review system is overburdened by the rising tide of submissions.
We analysed the number of requests required in 2001–10 to obtain a review; compared the number of submissions in 2001–07 with the number of unique reviewer names in each year; and calculated the mean number of reviews per reviewer in 2001–07 (see http://go.nature.com/68mh16).
The idea that it is now harder to find reviewers turns out to be true (the mean number of reviewing requests issued per review increased from 1.38 (s.e. = 0.02) in 2001 to 2.03 (s.e. = 0.05) in 2010). However, this seems to be due to changes in technology rather than to changes in reviewers' attitudes: the declining acceptance rate by invited reviewers strongly correlates with the 2008 transition from an e-mail-based editorial system to an automated one, perhaps because spam filters blocked e-mail invitations.
We also found that the reviewer pool expanded in proportion to the increased submission rate (which doubled between 2001 and 2007), yet there was no increase in the average number of reviews by individual reviewers.
The authors of the additional papers are the most likely source of the extra reviewers. Each Molecular Ecology submission has an average of 4.5 authors and decisions are based on an average of 2.7 reviews, so only 0.6 reviews per co-author are required to compensate for the review burden of each new article. These figures indicate that the reviewer pool still seems able to accommodate the increasing number of submissions.