There's a revolution going on in America's married couples: call it the rise of the breadwinning wives.

More women than ever are out-earning their husbands by significant margins, according to new data released by the U.S. Census. About 9 percent of wives earn at least $30,000 more than their husbands, marking a gain of 3 percentage points during the past 15 years. Another 11 percent of women earn between $5,000 to $29,999 more than their husbands. That means nearly one out of five wives is now earning a significant chunk of change more than their husbands are.

"This is a noteworthy development, given a broader context of an enduring gender earnings gap," Jamie Lewis, a statistician in the Census' Fertility and Family Statistics Branch, said in a statement.

Married women who earn more than their husbands tend to be white, college-educated and older, according to a Pew Research Center study published in 2013.There are two types of women who are now the breadwinners in their families, Pew noted: older, mostly white and educated women who are bringing home bigger paychecks than their husbands, and a second group of poorer women who are single mothers and are less likely to have a college degree.

While the breadwinning wife is gaining share in American households, it still holds true that more husbands are outperforming their wives when it comes to income. About 35 percent of husbands make at least $30,000 more than their wives, the Census said, although that's declined from 38 percent in 2000.

While the gender pay gap continues to have a stubborn foothold in the American workplace, there are signs that career prospects for women and men are changing. Women, for instance, are graduating from college at a higher rate than men, and a college degree is one of the most significant indications of higher lifetime income.

On the other hand, men's workforce participation has been declining since the late 1940s, when about 87 percent of adult men held jobs or were looking for work. Male workforce participation took a dive during the recession, and hasn't yet recovered -- as of October, it had dwindled to 68.7 percent of American men.

That's prompted questions from economists about why men aren't returning to the workforce: Is the trend due to declining job quality? Because of a lack of jobs in certain sectors? Because husbands might be opting out of the workforce if their wives make more money?

While it's not clear why men are leaving the workforce, there is another cultural change supporting women who earn more than their husbands. Even as recently as 1997, 40 percent of Americans said it was problematic for women to earn more than their husbands, Pew found. That share has declined since to 28 percent, with men with college degrees more likely to find it a non-issue if their wives earn more, Pew reported.