In my own experience at the ANU, only about 8-12% of Engineers in first year are female. How much of this is due to sex-based statistical differences in inate talent, how much due to socialisation, and how much is due to girls just being more interested in other areas? My bet's the last of the three, but that just begs the question: how much is inate, "natural", and how much is socially conditioned? I think the latter predominates by maybe 3:1, but the former exists too. We'll see. If I'm right, all of the curves will flatten at about the same time, with women getting a little more than half of all PhDs, but the relative proportions in the different areas remaining constant. That would mean about 30% of all engineers would be female - with a corresponding gender imbalance the other way in law, medicine, and the social sciences.
The graph is from Jonathan Kulick's excellent article on the subject, Math is Hard, in The Reality Based Community. The article also contains this little gem. Something that encapsulates - or encrapsulates - all that I despise in Post-Modernist Feminism.
The privileging of solid over fluid mechanics, and indeed the inability of science to deal with turbulent flow at all, she attributes to the association of fluidity with femininity. Whereas men have sex organs that protrude and become rigid, women have openings that leak menstrual blood and vaginal fluids. Although men, too, flow on occasion—when semen is emitted, for example—this aspect of their sexuality is not emphasized. It is the rigidity of the male organ that counts, not its complicity in fluid flow. These idealizations are reinscribed in mathematics, which conceives of fluids as laminated planes and other modified solid forms. In the same way that women are erased within masculinist theories and language, existing only as not-men, so fluids have been erased from science, existing only as not-solids. From this perspective it is no wonder that science has not been able to arrive at a successful model for turbulence. The problem of turbulent flow cannot be solved because the conceptions of fluids (and of women) have been formulated so as necessarily to leave unarticulated remainders.As he says - "Although this would have made Alan Sokal proud, it was not a hoax. Every woman fluid dynamicist I’ve shown this to has responded with an unladylike snort.".
(Hayles, N. K. (1992) “Gender encoding in fluid mechanics: masculine channels and feminine flows,” Differences: A Journal Of Feminist Cultural Studies, 4(2):16–44.)
Not just fluid dynamicists.