There is a tendency that this will lead the demographics of a field to pretty much stay the same over time. If you work in a field that is 90% men, only 10% of the people you have worked with are women, which means in the long run only 10% of people you'd end up referring would be women. This is definitely true in my case--the number of women whose technical skills I can vouch for went up considerably once I started working with more women.
That said, the Bay Area is weird and I've never lived there.
Also, admittedly, specifying "white males" was a misstep on ebiester's part. Whatever narrative there is about diversity in tech breaks down unless you stipulate that South and East Asians don't count as underrepresented minorities.
* White Americans: 91% of social network are white; 8% black.
* Black Americans: 83% of social network are black; 1% white.
[0] https://www.prri.org/research/poll-race-religion-politics-am...
And in Silicon Valley its different - the mix of international people of high education and achievement make it a skewed sample.