McKinsey did find that companies with a higher percentage of female outperform their competitors.

I mentioned this elsewhere in the thread, but I thought I would point out here that I checked the McKinsey web site for the city where I work -- New York. It seems that 84% of the senior managers in New York are men.

http://www.mckinsey.com/global_locations/north_america/northeast/en/our_people

I also checked their web site for California, it seems that roughly 80% of the senior managers are men:

http://www.mckinsey.com/global_locations/north_america/west_coast/en/our_people

Ditto for the Southern office:

http://www.mckinsey.com/global_locations/north_america/southern/en/our_people