Editors handle their collaborators' submissions despite explicit policies

Editors are crucial to the integrity of the scientific publishing process, yet they themselves could face conflicts of interest (COIs), whereby their personal interests interfere with their editorial duties. One such COI stems from the fact that, apart from a few exceptions, the vast majority of editors are research-active scientists with many collaborators. Each such editor could potentially handle submissions from their recent collaborators, allowing the editor to use their power, consciously or otherwise, to treat such submissions favourably, thereby jeopardizing the integrity of the editorial decision. Naturally, a number of policies have been put in place to govern such COI, but their effectiveness remains unknown. We fill this gap by analyzing half a million papers handled by 60,000 different editors and published in 500 journals by six publishers, namely Frontiers, Hindawi, IEEE, MDPI, PLOS, and PNAS. We find numerous papers handled by editors who collaborated recently with the authors; this happens despite policies explicitly prohibiting such behavior. Overall, nearly 3% of journals have a COI rate $\geq$ 10%, and nearly half of them have a COI rate $\geq$ 2%. Moreover, leveraging three quasi-experiments, we find that COI policies have a limited, if any, effect on regulating this phenomenon. Finally, we find that editors are faster to accept submissions from their collaborators, raising the possibility of favoritism. These findings highlight the need for policy reform to assure the scientific community that all submissions are treated equally.