Britain's Prince William and his wife Kate, Duchess of Cambridge, on their wedding day. A new study shows marriage is not as popular as it used to be.
Britain's Prince William and his wife Kate, Duchess of Cambridge, on their wedding day. A new study shows marriage is not as popular as it used to be. - 
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The rise of single-parent households isn’t just a social and cultural phenomena – it has important economic implications. That’s the gist of a new study put out by the conservative-leaning American Enterprise Institute, which argues that stronger marriages could help bridge the ever-growing class divide. But trying to pin down the root causes of the gulf between the haves and have-nots is a bit like trying to hit a moving target.

In 1980, approximately 78 percent of families with children were headed by married parents. In 2012, married parents account for only 66 percent of families with children.

Bradford Wilcox, director of the National Marriage Project and a co-author of the institute study, says this retreat from marriage accounts for 32 percent of the growth in family-income inequality between 1979 and 2012 – and particularly affects the poor and working class.

“So, not only are they earning less, comparatively speaking," says Wilcox, "but they’re also less likely to pool their incomes and to build common assets as married families."

On average, the data show that married men earn about $16,000 more a year than their single peers, Wilcox says. Likewise, children from married families were shown to be much more likely to earn a college degree.

Others say this "marriage effect" is a bit overblown.

“The big changes in distribution of income since 2000 have been near the top,” says Christopher Jencks, a professor of Social Policy at Harvard University's Kennedy School of Government. He says the massive growth in incomes by the "one percent" is a more plausible explanation for inequality.

“It’s a little hard to think that, 'well, that’s all driven by single-parent families.' That’s a big factor at the bottom [of the income scale], but the bottom hasn’t changed much," Jencks says.

He points to wage stagnation and fewer manufacturing jobs as other explanations for growing economic inequality.

Follow Adam Allington at @@aallington