For most of us, the process is happily invisible. You meet someone under a tree on an exclusive campus or during orientation at a high-powered professional firm, and before you know it, you’re twice as rich. But sometimes—Grandmother understood this well—extra measures are called for.
It is misleading to think that assortative mating is symmetrical, as in city mouse marries city mouse and country mouse marries country mouse. A better summary of the data would be: Rich mouse finds love, and poor mouse gets screwed. It turns out—who knew?—that people who are struggling to keep it all together have a harder time hanging on to their partner. According to the Harvard political scientist Robert Putnam, 60 years ago just 20 percent of children born to parents with a high-school education or less lived in a single-parent household; now that figure is nearly 70 percent. Among college-educated households, by contrast, the single-parent rate remains less than 10 percent. Since the 1970s, the divorce rate has declined significantly among college-educated couples, while it has risen dramatically among couples with only a high-school education—even as marriage itself has become less common. The rate of single parenting is in turn the single most significant predictor of social immobility across counties, according to a study led by the Stanford economist Raj Chetty.
This divergence of families by class is just one part of a process that is creating two distinct forms of life in our society. Stop in at your local yoga studio or SoulCycle class, and you’ll notice that the same process is now inscribing itself in our own bodies. In 19th-century England, the rich really were different. They didn’t just have more money; they were taller—a lot taller. According to a study colorfully titled “On English Pygmies and Giants,” 16-year-old boys from the upper classes towered a remarkable 8.6 inches, on average, over their undernourished, lower-class countrymen. We are reproducing the same kind of division via a different set of dimensions.