Well, whatever the population figures, something creates an overabundance of single men. This must create a drag on the reproductive rate. Also, what you're saying might apply to SF itself, but not necessarily to South Bay / Silicon Valley.

http://creativeclass.typepad.com/.shared/image.html?/photos/...

One other thought... even given a balanced overall population, we need to look specifically at those of reproductive age. Population figures will include children, which should be roughly 50/50 m/f, until they move away as adults (perhaps due to the high rents!).