And the divorce rate among college-educated women has plummeted. Of those who first tied the knot between 1975 and 1979, 29% were divorced within ten years. Among those who first married between 1990 and 1994, only 16.5% were.

At the bottom of the education scale, the picture is reversed. Among high-school dropouts, the divorce rate rose from 38% for those who first married in 1975-79 to 46% for those who first married in 1990-94. Among those with a high school diploma but no college, it rose from 35% to 38%. And these figures are only part of the story. Many mothers avoid divorce by never marrying in the first place. The out-of-wedlock birth rate among women who drop out of high school is 15%. Among African-Americans, it is a staggering 67%.

Does this matter? Kay Hymowitz of the Manhattan Institute, a conservative think-tank, says it does. In her book “Marriage and Caste in America”, she argues that the “marriage gap” is the chief source of the country’s notorious and widening inequality. Middle-class kids growing up with two biological parents are “socialised for success”. They do better in school, get better jobs and go on to create intact families of their own. Children of single parents or broken families do worse in school, get worse jobs and go on to have children out of wedlock.