The American dream can be put in a number, and that number has halved: 9 in 10 children born in 1940 grew up to out-earn their parents; for those born in the 1980s it is now about 1 in 2

The American dream can be put in a number, and that number has halved: 9 in 10 children born in 1940 grew up to out-earn their parents; for those born in the 1980s it is now about 1 in 2 — barely a coin toss

About 90 percent of American children born in 1940 grew up to earn more than their parents did at the same age. For children born in the 1980s, that share dropped to roughly 50 percent. That is the...