All (90%) of rationalist women who would not otherwise have become rationalist women became so because of Harry Potter and the Methods of Rationality.
I'm not sure that's true. When I looked in the 2012 survey, I didn't see any striking gender disparity based on MoR: http://lesswrong.com/lw/fp5/2012_survey_results/8bms - something like 31% of the women found LW via MoR vs 21% of the men, but there are just not that many women in the survey...
That does not factor the main point " that would not otherwise have become rationalist" There are loads of women out there on a certain road into rationalism. Those don't matter. By definition, they will become rationalists anyway.
There are large numbers who could, and we don't know how large, or how else they could, except HPMOR
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.