Reviewer rings: how a small circle controls a field
In closely-bounded subfields, a handful of reviewers can gate virtually every submission in a year. It is not a conspiracy. It is mathematics: a field with three hundred active authors and twelve qualified reviewers will re-encounter the same twelve reviewers in round after round of editorial assignment.
That structure is, on its own, benign. It is also the ideal substrate for a paper mill: infiltrate a reviewer position in a small editorial board, and you gain asymmetric leverage over acceptance decisions for the whole subfield.
We started mapping reviewer networks in materials science earlier this year. The early picture is worse than we feared. More in a forthcoming piece.