I’ve had quite few searches land here looking for the male to female ratio in Silicon Valley. I found a site by some Stanford students with apparently little else to do that gives statistics on the ratio in bars. Now, they are probably a bit skewed because bars generally cater to specific age groups. They found the odds to be 5:3 (male to female) and 3:1.
I am also borrowing a cartoon they have on their site which sums up dating out here perfectly. I wish I had thought it up.

This describes life outside the university as well. I’ve worked as an engineer and seen the odds first hand.