Mr. Hout’s paper adds to a growing body of research on the dimensions of socioeconomic inequality in the U.S. Stanford University economist Raj Chetty found in a December 2016 paper that the ratio of Americans who earn more than their parents fell to 50% for children born in the 1980s from 90% for children born in the 1940s. https://blogs.wsj.com/economics/2018/09/03/parents-jobs-increasingly-shape-how-far-kids-get-in-life/In many cases, upward mobility as defined by Mr. Hout would hardly be noticed by a layperson. One point on the author’s scale corresponds to the difference between a receptionist (26 points) and a hairdresser (25 points). A 15-point improvement—from food-preparation worker to medical assistant, for example—is more perceptible but has also become considerably rarer. So-called “long-distance mobility” from one generation to the next declined from 37% of men born in 1945 to 22% born in 1985.