Dissecting the Global Peer Review Ecosystem: Skewness, Homophily, and Diversity Dynamics

Peer review is crucial to the knowledge production system and publication quality control. However, limited research has been conducted on the characteristics of anonymous reviewers and the connections between journals and reviewers. Based on the journal-reviewer-coupling relationship of 477,684 reviewers and 6,058 journals from Publons, we show a highly concentrated review network with a small number of journals relying on a disproportionately high share of reviewers. The skewness in reviewer distribution is evident at various levels: journal field, country of origin, and journal impact. Moreover, we revealed significant disparities in reviewer background: Women review for fewer journals and are underrepresented among reviewers, especially in fields such as physics and mathematics and in countries such as China and Japan. Journals in fields like psychology, health, and humanities tend to rely on reviewers from a limited geographic location pool, and those based in Brazil and Japan often connect with local countries' reviewers. We also observed homophily effects, where journals across fields, countries, and with higher journal impact tend to share reviewers mutually. Our study provides a more comprehensive understanding of the global peer review system and highlights the need for greater diversity and inclusion in the peer review process.