Based on my own anecdotal experience with hiring developers, the m/f ratio is highly unbalanced before our own biases even come into play. A while ago, we had a recruiting agent helping us to find candidates, based solely on a list of technical criteria. She (yes, she) sent us almost only men, a dozen or two of them. The one exception was a woman who choked on the fizzbuzz test. That was actually really saddening.