Over the weekend a letter from a Princeton alumna and mother named Susan A. Patton went viral. In it she advised current Princeton female students to “find a husband on campus before you graduate.”

She explains her reasoning:

Men regularly marry women who are younger, less intelligent, less educated. It’s amazing how forgiving men can be about a woman’s lack of erudition, if she is exceptionally pretty. Smart women can’t (shouldn’t) marry men who aren’t at least their intellectual equal. As Princeton women, we have almost priced ourselves out of the market. Simply put, there is a very limited population of men who are as smart or smarter than we are … you will never again be surrounded by this concentration of men who are worthy of you.

O.K., so there are a lot of controversial issues in her letter, which has been called regressive and much worse. But the idea that women may have stronger preferences than men do for assortative matches — that is, for marrying mates who are like them — has a long literature in economics and to some extent has been supported by data.

That said, it seems as if preferences for assortative matching are increasing for both genders, particularly as more women join the labor force (and therefore become more likely to have the same wage profile as their prospective partners, at least compared to women a couple of generations ago). One unintended consequence of more likes marrying likes is higher income inequality; the rich and educated marry the fellow rich and educated and get richer together, while the poor and uneducated generally don’t get married at all, remaining poor and alone.

What about Ms. Patton’s assertion that men are willing to overlook “a woman’s lack of erudition, if she is exceptionally pretty”?

A paper published last year in the Journal of Political Economy actually tried to quantify the trade-off that husbands make between beauty and brains when choosing a mate. Using longitudinal survey data on married American couples, it found that women can compensate for two additional units of body mass index with one more year of education. In other words, it’s all right for women to be a little heavier if they’re also a little more educated, or a little less educated if they’re also a little skinnier.

Male physical attractiveness matters, too. But for men, the stronger trade-off seemed to be between weight and wages: Men may compensate 1.3 additional units of B.M.I. with a 1 percent increase in wages.

Addendum: I should note that long before Ms. Patton’s letter made it to the nightly news, Princetonians seemed exceptionally prone to assortative matching. According to a Daily Princetonian article from 2002, 26 percent of female graduates and 12 percent of male graduates married a fellow Princetonian. The share was larger for women because the universe of Princeton alumnae is smaller than that for Princeton male alumni, since Princeton’s first female graduates were admitted in 1969.