Thats very false. Here is a sample of companies and their ratio:
Google: Median Age 29 years Gender Male 65% Female 35%
Yahoo:
Median Age 32 years Gender Male 66% Female 34%
Facebook:
Median Age 27 years Gender Male 68% Female 32%
Sun:
Median Age 37 years Gender Male 74% Female 26%
eBay:
Median Age 32 years Gender Male 62% Female 38%
Non Tech:
UC Berkeley (employees):
Median Age 29 years Gender Male 51% Female 49%
City of San Francisco:
Median Age 32 years Gender Male 62% Female 38%
