I haven't seen any studies about general men and woman, the only study I've seen is that men seem to have a wider distribution than women -- this was offered to explain why men seem to dominate certain fields.  This is not saying that men in general are better at math, just that the underlying probability distributions are different and it might not be reasonable to expect a 50/50 split at the top of a given field.  The underlying distribution might 60/40 or 70/30.  Just as the prison populations, and serial killer rates are different.