I haven't read the whole thread, but a quick comment: I was involved a few years back with an international women in mathematics organisation, and it rather informally collected information about the proportion of women at various levels from undergraduate maths up to professor. We were struck by the variation in the figures; southern Europe was very noticeably better than northern Europe for example. One of my colleagues produced an aha moment in a meeting by noticing that what was happening was that proportion of women was low in countries where maths was considered a high-status subject, one many of the cleverest people would go into, and high in countries where it was considered a low status subject (e.g. apparently, in some of the southern European countries, it would be weird to go into maths if you had the ability to go into engineering). As far as we could tell, it wasn't that those of us who had fewer women students had higher quality students, either - IOW this really looked like a social, not an intellectual, phenomenon.
Another interesting phenomenon is the precipitous fall in the proportions of women entering computer science since computers became ubiquitous in schools (later, homes). It looks as though that made it a boy's subject, whereas before it had been fairly neutral.
