I am still slowly working my way through the text and tables in the recent AAUP report (AAUP Faculty Gender Equality Indicators 2006), but one thing that struck me right away was the drop-off in number of women from the Associate to Full Professor levels. On p. 11, the text says "Thus, promotion to full professor constitutes a further point where inequities persist in the career progrssion of faculty women."
There are so few women in my field that my personal (anecdotal) database is small, but I think women lose out at this stage in two different ways:
1 - I know several women who have stalled at the associate professor level because they don't have sufficient papers, grants, or international repute. By the current standards of our field at a large research university, these women do not meet the standards for promotion. BUT, I can think of many many men who have been promoted to full professor with similar moderate to low levels of productivity.
2 - I know several women who were not promoted despite numerous grants, publications, etc. (and high quality teaching). These women could sue, but instead most have accepted offers at other institutions that will value them for their excellence.
1 year ago