Gender ratios greatly affect mating markets (pools of people in an area trying to date each other, e.g. the student body of UC Berkeley, or single, college-educated heterosexual people in Manhattan). When gender ratios start to become unbalanced (i.e. a gender ratio of roughly 60:40 or more extreme), the less-common sex starts to have a huge advantage in dating.

Effects of an unbalanced gender ratio:
-The scarce gender becomes far more selective, and people who would be overlooked in a normal mating market suddenly have a ton of power.

-The plentiful gender becomes industrious. It’s hypothesized that:
1) part of China’s economic boom is because the lopsided gender ratio (with more men) has lead more men to become entrepreneurs; and
2) the women’s movement in the U.S. was driven, in part, by the scarcity of college-educated men with whom the smart women could pair up with.
(Note: the author isn’t implying that the women’s movement wouldn’t have happened at all if their had been more date-able men, just that an increased focus on career is common in cohorts of women when there are fewer men.)

-When there are more men, monogamy tends to be more common, with men competing for female attention. When there are more women, hookups tend to be more common, with women competing for male attention.

Auction theory:
[Note from Steve: It never occurred to me that auction theory would exist, but it makes sense. It involves lots of money and high emotional stakes, so of course it’s going to be an interesting field of study for behavioral psychologists. Read more here.]

There are strong bidders and weak bidders. Weak bidders aren’t confident, so they bid aggressively in the early rounds of the auction to ensure they get something. Strong bidders, by contrast, are confident, so they hold out until the later rounds to bid on the high-value items. Think of an art auction. If you’re the richest person, you’re likely going to hold out till the end for the one Van Gogh painting, rather than tipping your hand early for the Watteau’s or the Troost’s. 

Similarly, very attractive and smart women are going to hold out for very attractive and smart men, while women who are less confident in their ability to secure a partner are going to try more aggressively to do so. When you combine this with lopsided gender ratios (in this case, more women), you get a ton of very attractive women who are single in their 30’s.

If that still doesn’t make sense, here’s an explanation by analogy: If you start playing musical chairs with 25 people and 24 chairs, there’s a good chance you’ll get a chair in the first round. In the last round though, there’s 2 people and 1 chair. A 50% chance of success, versus the 96% chance you had before. So if you’re one of 150 women in a group of 100 men, odds are decent you’ll find a partner if you try to find one in the beginning, but the system will eventually have 100 couples and 50 single women. You’re punished for waiting. (That analysis ignores death, breakups/divorce, etc., but you get the idea.)

Other things I thought were interesting:
Preferences for attractiveness:
Research suggests that women care more about the attractiveness of the plentiful gender and less about the attractiveness of the scarce gender. When men are plentiful, women can be selective and care more about male attractiveness. They don’t care as much about what their competition looks like. When women are plentiful, they become less selective and care less about male attractiveness. They care more about what other women look like, because they need to size up their competition. [There was a small sample size (n=100) for the study that drew these conclusions, so take this with a grain of salt. It makes intuitive sense, though. The study was done with only female participants.]
 
Mormons and Jews:
The book examines the Mormon community and the Orthodox Jew community to see if the effects of lopsided gender ratios were nullified by cultural values (in this case, both cultures strongly value marriage and monogamy). Both cultures, which had too many single women, saw similar effects to the secular community: men delayed marriage and shopped around more, even if that didn’t mean more casual sex (although I wouldn’t be surprised if this were happening secretly).

The Orthodox Jew community (that almost exclusively intra-marries) is the more interesting example though, because they have a control group where there’s a roughly equal gender ratio: Hasidic Jews. Yeshivish Jews (who have a crisis of too many single women) are very similar culturally to Hasidic Jews, but with one important (for our purposes) difference: male Yeshivish Jews tend to marry down in age, while male Hasidic Jews tend to marry women who are the same age as them.

Because there are approximately 4% more Yeshivish Jewish babies every year, this means that there are more women than men, as far as marriage-aged men are concerned (e.g. there’s roughly 100 22-year-old men for every 112 19-year-old women). The Hasidic Jews have a similar growth rate, but it doesn’t affect them because there are an equal(ish) number of men and women in each cohort. 

Golden Cock Syndrome:
Men at Sarah Lawrence University are said to have “Golden Cock Syndrome”, because women fawn all over them. Why? The student body is 75% female (i.e. there are 3 women for every 1 man), one of the highest percentages in the country.

The author’s recommendations:

1. Make gender ratio a consideration when choosing a college.
2. Be aware that holding out is a risky strategy for college-educated women. (See the discussion on auction theory.)
3. Your workplace is part of your dating ecology, so choose your career judiciously.
4. Go West, Young Woman. (There are plenty of places in the West, like San Jose and Seattle, that are good for women, compared to places like Manhattan, which is great for men. Check out dating by county and dating by state for a more detailed breakdown. Note this data is as of 2012.)
5. College-educated women should consider expanding their dating pool to include lesser-educated men.

None of this is to say that should base your decision on where to live/work solely on how easy it will be to find a mate. Dating success can have a big impact on your mental health though, so don’t overlook it. Example: if you’re a woman who can’t decide between going to University of Georgia or Georgia Tech, you could use the relative gender ratios of the schools as the tiebreaker. Georgia Tech skews male to a much greater extent than University of Georgia, so it’s a better mating market for women.