I haven't looked into the statistics of it, but it seems that in Asia women in math or science fields are more common than in the West. My wife is Asian and was a CS major and was the top of her class. I've met a lot of her friends from university and they almost all seem to be quite intelligent and know their stuff. Back a long time ago when I was attending university in the States, there weren't many women that I saw who were CS, EE, or other science majors and the ones that I was aware of were no where near the top of the class.
It seems to me that in Asia a lot more emphasis is placed on education than in the West, so perhaps that's the reason I see more women in science/technical fields in Asia. Parents really push their children, both men and women, to get a good college education in a field where they can get a good job after graduating.