For why so few girls major in computer science in college, below is my answer.

http://news.ycombinator.com/item?id=2111651

So, a typical scenario is a boy in middle school who is really excited because he just understood how an automobile differential (TCP part of TCP/IP, binary search, virtual memory, etc.) works and with great excitement tries to explain it to a girl his age at, say, lunch, and we have a strict dichotomy: The boy is totally clueless that the girl couldn't be less interested. The girl sees right away that she couldn't be less interested, not to offend the boy unduly pretends to be a little interested, and sees in clear terms that the boy is totally clueless at perceiving her lack of interest. She concludes that he is so clueless he is really easy to manipulate (a fact she suspects could be useful and saves for later). The boy doesn't understand the girl, and the girl regards the boy, and soon, all boys less then 2-6 years older than she, as at least 'socially' immature and, really, just immature. She wants nothing to do with such 'children' (she already understands that a woman needs a strong man) and will concentrate on boys 2-6, maybe 8 or 10, years older than she is. She has a point: She was likely more mature socially at age six than he will be at age 16.