Kathryn Norlock (Trent) sends along 2009 data on the percentage of women teaching philosophy at the postsecondary level (from this source, Table 256):  women are 16.6% of the 13,000 total full-time philosophy faculty (that is, 2,158) and 26% of the 10,000 part-time instructors (that is, 2600).  All together, women comprise 20.69% of postsecondary philosophy teachers in the US as of 2009.    The percentage of full-time faculty who are female is quite a bit lower than I realized, and shockingly so.