The G.I. Bill may have helped lower assortative mating, because it gave opportunities for upward mobility to economic classes that had not enjoyed it. In general, the greater the number of men entering the middle class, the more socioeconomic mixing will occur.

In 1950 it was also the case that marriage ages were especially young, meaning that couples often paired off from high school and may have had less of a sense how to match to each other by expected income or education. And most women had fewer chances to earn very much, so few if any men were searching hard to find future law partners or doctors.

Economics itself shows patterns of assortative mating. In 2007, an article in The New York Times cited 13 up-and-coming economists, most of whom have gone on to greater fame. The striking fact is that six of these individuals are married to each other, and that was not the premise of the article. Another person on the list, Justin Wolfers, is a partner with another prominent economist, Betsey Stevenson, with both working at the University of Michigan. (They have two children together but are not legally married; Professor Wolfers is a frequent contributor to The Times.) The children from these kinds of pairings probably have a head start when it comes to pursuing successful careers as research scientists or in other education-intensive endeavors.

Universal preschool, further experiments with charter schools, and higher subsidies or tax credits for children are among the policy innovations that might lift opportunities for children of lower earners. Even if those are good ideas, it is not clear how much they can overturn the advantage that comes from being a child of highly educated, highly motivated parents with lots of will and also money to spend on lessons, outings, travel and other investments in the future of their children.

Today, we rightfully reject the idea of eugenics as repugnant, yet we are conducting our own experiments in mating, without much careful thought as to where they will lead. Match.com and Tinder help us find “just the right mate,” according to our prior desires and specifications, with aid from computer algorithms. The real question may be not whether we can reverse some of the less desired effects of assortative mating, but rather just how far the practice will go.