Of college-educated people who married in the early 2000s, only about 11 percent divorced by their seventh anniversary, the last year for which data is available. Among people without college degrees, 17 percent were divorced, according to Mr. Wolfers.

Image Gwyneth Paltrow and Chris Martin a few months before their breakup. Credit... Colin Young-Wolff/Invision/AP

Working-class families often have more traditional notions about male breadwinners than do the college-educated — yet economic changes have left many of the men in these families struggling to find work. As a result, many wait to achieve a level of stability that never comes and thus never marry, while others split up during tough economic times.

“As the middle of our labor market has eroded, the ability of high school-educated Americans to build a firm economic foundation for a marriage has been greatly reduced,” said Andrew Cherlin, a sociologist and author of “Labor’s Love Lost: The Rise and Fall of the Working-Class Family in America.” “Better-educated Americans have found a new marriage model in which both spouses work and they build a strong economic foundation for their marriage.”

Some of the decline in divorce clearly stems from the fact that fewer people are getting married — and some of the biggest declines in marriage have come among groups at risk of divorce. But it also seems to be the case that marriages have gotten more stable, as people are marrying later.

Ultimately, a long view is likely to show that the rapid rise in divorce during the 1970s and early 1980s was an anomaly. It occurred at the same time as a new feminist movement, which caused social and economic upheaval. Today, society has adapted, and the divorce rate has declined again.

In the 1950s and 1960s, marriage was about a breadwinner husband and a homemaker wife, who both needed the other’s contributions to the household but didn’t necessarily spend much time together. In the 1970s, all that changed.