my experience: Where I work, on my floor we are either a proportion of 50% - 50% or 40%-60% (in favor for the Girls). Hey, but this is Romania, we don't have feminist movements and so on. Different society. Even in college we are something like 40%-60% (males win here) but we don't take it as a big deal... Btw found CS girls in college that were smarter than me on some fields of this domain :), and I know where to ask if I have a question about those fields.

other answer: Depends on the "society" although while I was in the USA everybody was blaming it... and believe me is not because of it, is because of those who like to blame it ;).

Last but not least... my girlfriend is a developer.