Vivek Wadhwa is doing a bunch of research into the data. I don't have his report at my fingertips but fundamentally, not investing in women is not a rational move. Here's the media headline version:
"Women-led private technology companies are more capital-efficient, achieve 35 percent higher return on investment, and, when venture-backed, bring in 12 percent higher revenue than male-owned tech companies."
Source: http://www.businessweek.com/articles/2013-02-20/women-who-ru...
Conclusion: Women earn over 50% of degrees but start fewer than 3% of companies. If we accept that women-led companies do well, as per the data -- and yes, there are certainly caveats -- then this gap clearly shows there is a problem, in terms of inefficient use of investment if nothing else.