Personally, I've long thought that there was no difference in ability with math between men and women: only an interest in pursuing higher-level math. It's the same with physics, computers, engineering, etc... as much as there's concern about equal numbers of enrollments, maybe people should just take a step back and ask themselves "why?" when it's obvious women aren't generally as interested in those subjects as men.

Taking several steps back, educational studies in general are showing that girls are consistently over-performing same-aged boys in school in all categories... except maybe gym.

Oh, and for the record, I've known some extremely talented women in math so I don't believe for a second that they're "less able". Probably the smartest math professor I ever had was a woman who quit teaching to go work on hush-hush projects for the NSA.