In the past 10 years, the percentage of American marriages that end in divorce has fallen, and in a new paper, the University of Maryland sociologist Philip Cohen quantified the drop-off: Between 2008 and 2016, the divorce rate declined by 18 percent overall.

After accounting for the rising average age of married Americans and other demographic shifts during that time, Cohen found “a less steep decline—8 percent—but the pattern is the same.” That is, the divorce rate in 2016 was still lower than one would have predicted if the demographics of married people were the same then as in 2008.

When I asked Andrew Cherlin, a sociology professor at Johns Hopkins University, how to make sense of this trend, he opened his explanation with something of a koan: “In order to get divorced,” he said, “you have to get married first.”

Marriage has become a trophy.

The point he was making was that people with college degrees are now more likely to get married than those who have no more than a high-school education. And the key to understanding the declining divorce rate, Cherlin says, is that it is “going down some for everybody,” but “the decline has been steepest for the college graduates.”

The reason that’s the case is that college graduates tend to wait longer to get married as they focus on their career. And they tend to have the financial independence to postpone marriage until they’re more confident it will work. This has translated to lower rates of divorce: “If you’re older, you’re more mature … you probably have a better job, and those things make it less likely that you’ll get into arguments with your spouse,” Cherlin says.