Hi David, I found a couple of more comprehensive blog posts.  Evelyn Brister reports that the number of women in philosophy is just below 21%.  She did a rough count by gender of the names appearing in the APA's membership directory in 2004.  She also compared her findings to other stats which suggest that there are just below 21% women in philosophy.  I think the numbers are lower than 21% if you include the numbers from community colleges and other forms of employment for philosophers.  But I will have to see if I can find posts that discuss this.  The other posts, also by Evelyn Brister, discuss related issues (women who earned a Ph.D. in philosophy, women who earned a bachelor's degree, etc.).

http://knowledgeandexperience.blogspot.com/2007/12/women-in-philosophy-data-on-professors.html

http://knowledgeandexperience.blogspot.com/2007/11/women-are-not-earning-more-philosophy.html

http://knowledgeandexperience.blogspot.com/2007/11/bachelors-degrees-in-philosophy-by-sex.html

http://knowledgeandexperience.blogspot.com/2007/12/why-arent-there-more-women-in.html