One important lesson from Stevenson and Wolfers is that, as much as it feels like things are changing very rapidly, a longer view on marriage trends reveals a more boring picture. If you pull back the lens, not to the 1960s but to the 1860s, the marriage rate and the divorce rate stick stubbornly to long-term trend lines.



Marriages-per-thousand people are declining, but slowly, after spiking in the 1940s. Divorces-per-thousand people are rising, but slowly, after spiking in the 1970s. Even in the Great Recession, which theoretically scared couples from investing in matrimony, we've seen "the same rate of decline that existed during the preceding economic boom, the previous bust and both the boom and the bust before that," Wolfers wrote.

The median age of marriage for men and women is rising slowly into the high-20s. But that's not so unique compared to men's historical averages. What is new -- really, really new -- is the rising marriage ages for women.



The education revolution for women -- one of the happiest trends of the 20th century -- carries important implications for the marriage market. First, if women are going to college, more of their 18-22 years will be taken up by history classes rather than husbands. Second, when these women start earning money, fewer need to marry for financial reasons, which means they can afford to put off marriage. Thanks to birth control, a little bit of biotechnology has helped their cause by reducing the costs of being sexually active and single.

THE TWO MARRIAGE TRENDS



The economics of marriage suggest it's like any other investment. Women are more likely to get hitched when they see big potential gains from a union. That explains why the apparently monolithic Decline of Marriage is in fact two polar opposite trends. The first points toward the revitalization of marriage. The second points to decline.



First, for highly-educated or rich women, marriage rates are actually rising. It was once the case that a college degree was the equivalent of punching your spinster card. In the late 1800s, half of all college-educated women never married. But in the last 40 years, marriage rates have increased for the top 10 percent of female earners more than any other group, Michael Greenstone and Adam Looney found in a new report from The Hamilton Project. A 2004 American Community Survey also found college-educated women were 10 percentage points more likely to be currently married than women with less education.

Second, there is a parallel trend that really does look like the crumbling of marriage. Among less-educated and poorer women, marriage is in outright decline. The bottom half of female earners saw their marriage rates decline by 25 percentage points, Greenstone and Looney find and show in the graph above.



There is evidence that social and economic sorting in America creates clusters of people who match up by education, salary, and politics. As a result, perhaps poor or under-educated women are more likely to be matched with poor or less-educated men who offer a worse return on the marriage investment.

