In other words, increase the number of males in a system too much and the number of females interested in pairing up GOES DOWN, due to some mysterious psychological trigger. The way I have been describing it, for those who are curios, is if you grabbed 100 young people off the street at random and put them in a big auditorium, you would have lets say 55% male and 45% female. The remaining 10 women are now happy, as they have men fighting over them.
Women won't pick and choose, they won't choose at all. So 100% of the women are either in a relationship, or know they could very easily get into one and are happy and feel wanted, and over 1/3rd, or 20 out of 55 men stay lonely and feel rejected ll the time.
Second, and more puzzling, there is widely-shared belief among females that very few eligible/desirable men live in San Francisco.
Like it was mentioned, just ask any young single guy and they'll agree. I do photography and have covered clubs and events while in college so I've been witnessing it first hand.
Similarly a 2004 article in the magazine San Francisco estimated that unmarried straight 20 to 44-year-old men in San Francisco (not including Silicon Valley or Man Jose) outnumbered their female counterparts by about 12,000.
Yet two anecdotal curiosities give us pause: first, an informal study of male opinion and the SF night-life scene describes a ratio that is FAR worse than even the data suggests.
Add to this fact that America has the highest rate of overweight people in the world (50% of Americans are overweight) and you have a dating nightmare for men!
I live in the SF area so I can completely vouch for that article.