When demographers talk about how educated a city or place is, they often refer to the percentage of the population with a 4-year college degree. This may seem crude, but so far it has been found to be one of the best predictors of higher income levels and overall urban prosperity.

When you add in the fact that people tend to marry people that are similar to themselves – often called assortative mating – you get a driver for income inequality. People with high incomes are marrying other people with high incomes.

In this recent New York Times article they dive into the sorting that can happen even within colleges, including elite colleges. 

According to data from the Equality of Opportunity Project, if you were born between 1980 and 1984, went to Princeton, and came from a family with a household income in the top 20%, you had a 56% chance of being married by the time you hit 32-34 years old.

However, if you came from a family with a household income in the bottom 20%, you only had a 34% of being married by the time you hit the same age bracket. One possible explanation is that if you’re from a lower income family, you simply aren’t privy to the same “clubs”, where people mate, even though you still got into Princeton.

To reinforce this point even further, the above data suggests that only about 1.3% of Princeton students that come from a poor family will ultimately end up a rich adult. About 72% of Princeton students come from a household in the top 20 percent.

When I look at the numbers for Penn, my alma mater, the marriage spread isn’t quite as dramatic. The marriage rates are 55% and 48%, respectively, for the top and bottom 20%. Maybe that makes it more egalitarian. Or maybe not.