One of the great changes in American life over the last half-century is the decline of marriage. According to census figures, in 1960, 87% of 30- to 50-year-olds in the US were married. By 2015, only 60.5% were.

But the decline isn’t evenly distributed. In a recently released paper (paywall), “Women, Work and Family,” the economists Francine Blau and Anne Winkler point out that women with college degrees have seen the smallest change in marriage rates of any gender and level of education. College-educated women went from being far less likely to marry than less educated women, to being much more so. The pattern is similar among men, but not as dramatic.

Richard Reeves and Isabella Sawhill, researchers at the Brookings Institution’s Center on Children and Families, believe that highly educated women have had the smallest marriage decline, in large part, because they remade marriage into a more appealing institution. These educated, economically independent women now demand men who are interested in more equitable partnerships.

“In the past, highly educated women faced an unenviable choice between accepting a patriarchal marriage or forgoing marriage and children entirely,” Reeves and Sawhill write. “Now they are able to raise their children within a stable marriage without compromising their independence.” In an article for The Atlantic, Reeves notes that such unions are focused on “high-investment parenting” (HIP), rather than romance, sex or money.

One result of the college-educated woman’s relatively high propensity to marry is that it’s now much more common for a married woman to make more money than her husband. According to the US census, the proportion of opposite-sex marriages in which the woman brought in more income than her partner almost doubled from less than 15.9% in 1981 to more than 29.3% in 2015.