Women have stormed the academy in most fields, and around half of new medical doctors are female. I think it's time to retire knee-jerk sexism as the main explanation for the lack of women in tech.
While I'm confident that women face more barriers than men, it's dubious that sexism is sufficient to explain such extreme numbers. The same goes for math professors, Wall Street traders, and the NBA for that matter.
More smart women choose to become doctors or lawyers, it seems, than to study physics or to roll the dice on a startup. And a lot of those 25-to-40 year old women want to have a baby and raise a family, even if it means a less resume-impressive career. (My sister, an M.D. who specifically chose a family-friendly ophthalmology specialty, is one of them.) And what's wrong with that?
Traditionally speaking, don't most people have (their own) kids and raise families? If so, then post-menopausal women have significantly less "value," whereas a childless man hitting jackpot at age 70 can still build a new one from scratch.
If having a family fits into one's life equation, the strategies involved are much different, sexism or not.
Or the fact that many, many people (men and women) look at any woman between 25 and 40 and expect them to leave to have a baby and raise a family?