There is a present imbalance in the regional distribution of the burden of peer review. The regional distribution of reviewers (or, more specifically, of those invited to review) does not mirror the regional distribution of submitting authors. This is the conclusion of multiple studies (Kovanis, 2016 and Mulligan and van Rossum, 2014), including a study conducted by Wiley in 2016 (Warne, 2016). This research found that uneven burden upon researchers from the USA, providing 33-34% of the reviewers and 22-24% of the submissions.

One might argue that this is not an issue. Editors are under no obligation to ensure an even geographic distribution of those they invite to review. The primary consideration for editors, when selecting reviewers, must be choosing individuals whose expertise is appropriate to the manuscript under consideration. However, there are reasons for seeing the present imbalance as a problem. The burden of peer review is currently borne by a small pool of reviewers, leading to increased difficulty for editors in finding available reviewers (Sipior, 2018). Furthermore, there is an inherent advantage in having a diverse reviewer pool to counter tendencies toward group-think and bias.

Why This Imbalance?

We wanted to understand why there is this regional imbalance. Non-US researchers are willing to review (Mulligan and van Rossum, 2014); the problem seems to be that they are not being invited. We wanted to investigate the factors involved in the reviewers being invited and agreeing to review. Our hypothesis was that there would be a correlation between the location of the editor-in-chief (EiC) and the location of the reviewer. We also wanted to look at other potential factors, including the location of the author, the ranking of the journal, the size of the journal, and the apparent difficulty the journal had in obtaining reviews.

We selected two subject areas to look at, Medicine and Agricultural & Biological Sciences, and then downloaded the data from ScholarOne Manuscripts. The data was anonymized and then analyzed. Our research evaluated 149 journals, involving 55,732 articles and 208,084 invitations to review to 110,053 reviewers. Of these invitations, 105,235 (51%) were accepted, 57,181 (27%) were declined and 45,668 (22%) received no response.

How Do EICs Choose Reviewers?

Our findings endorsed earlier investigations that have revealed an imbalance between the locations of the corresponding authors (as declared in the author affiliation) and the locations of reviewers. In total (the entire data set), 25.68% of authors come from Asia, but only 9.08% of reviewers. 33.23% of authors come from Europe, but only 27.97% of reviewers. 23.85% of authors come from North America, and 31.7% of reviewers.

In addition we found that EiCs select reviewers from their own region more often than from other regions (with the exception of EiCs in Oceania.) The finding was repeated at a country level; EiCs more frequently select reviewers from their own country than the average. This is particularly notable for the Scandinavian countries, USA, Germany, and UK. EiCs from the USA, for example, select 50% of reviewers from the USA, compared to the average of 38%; and EiCs in the UK select UK-based reviewers twice as often as the average (22% compared to 11%). However, all EiCs show a preference for US-based reviewers.

The other factor where we found a clear correlation was between the location of the corresponding author and that of the reviewer. This was particularly notable for articles with Chinese, USA and Iranian corresponding authors. At a regional level, it seems that a very high proportion of those papers being sent to reviewers in Asia have Asian corresponding authors (55.9%). Similarly, reviewers in Africa are being sent a high proportion of papers with African corresponding authors. So, whilst there seems to be an overall preference for reviewers from the USA (a greater proportion of the total review invitations are sent to reviewers based in the USA), there is also a preference for sending papers to reviewers from the same region and country as the authors.

We did also find some indications that reviewers were more likely to accept invitations, and more likely to give positive reviews, in cases where they were from the same region as the corresponding author. The effect was small and would warrant further research.

None of the other factors we looked at seemed to correlate significantly with the location of the invited reviewer.

What Do These Findings Show?

Given these findings, we hypothesized as to why editors prefer reviewers from their own location and/or from the same location as the author. Our intuition is that this is due to the way editors select reviewers, which (anecdotally) is still primarily from their own networks rather than favoring other reviewer finding strategies, such as following citations or automated searches. There may be other factors as well. One way of assessing the suitability of an unfamiliar reviewer is by looking at the institution he/she is affiliated with; if editors are unfamiliar with institutions in other regions they may feel uncertain about using that reviewer. Our results also may suggest that editors may purposefully select reviewers from the same location as the author, which would make sense in cases where there is a geographically specific component to the research.

How Do We Find a Better Balance?

If our intuitions are correct, then moving towards a more regionally balanced reviewer pool would require adopting new strategies for finding and assessing reviewers. The knowledge and expertise of the editor, and his/herown personal networks, are an essential component to the peer review process. With the sheer volume of research being produced annually, it is increasingly unrealistic for editors to be connected with everyone working their fields. Using automated tools to search research articles has now made it possible for editors and those that assist them to identify qualified reviewers without any prior personal connection. Crucially, such tools identify reviewers based purely on their relevant publication history and are blind to their region (or any other demographic factor).

The future of peer review is better peer review, with impartiality at its core.

What are your thoughts on regional diversity in peer review? Let us know in the comments below.

Our research is published in Learned Publishing and can be found here.

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