Is it Seniority Bias or Gender Bias?

PhysioProf was recently discussing a figure from the NIH Extramural Data Book which pointed to a poorer success rate for women submitting competing continuation applications but not for new projects. His title “Old Boys’ Network Favors Men’s Continuing Grants?” was perhaps intentionally rich since as I pointed out in the comments, these results could be explained more by the “Old” part of the descriptor than by the “Boy’s” part. Additional data from the NIH Data Book provide more support for the seniority hypothesis.