Eric Schwitzgebel and his collaborator Joshua Rust have used a unique set of data to analyze promotion rates of men and women in philosophy, concluding that women in recent cohorts are not advancing to tenure as quickly as men.
Take a close look at the figures for philosophers with birthyears between 1970 and '79!
1970-1979 (57 professors.):
81% male (2% full, 11% assoc., 74% asst., 13% non-TT)
19% female (0% full, 18% assoc., 45% asst., 36% non-TT)
This valuable study clearly involved a significant amount of legwork (so to speak). More comments on it at Feminist Philosophers.