The research, which was released by the National Center for Family and Marriage Research at Bowling Green State University in Ohio, found that 40 percent of wives in two-income households contributed a greater share of income as of 2011, compared to 38 percent in 2006.
"Some of that has to do with the fact that men lose their jobs or are rehired into less well-paying jobs. It's not that women are earning more in an absolute sense but earning more because their mates are earning less," says historian Alice Kessler-Harris of Columbia University in New York in an interview with USA Today.
In addition, Jerry Jacobs, a sociology professor at the University of Pennsylvania, tells the paper that the difference might not represent a lasting change, because there's no way of telling why women earned more in 2011.
"Let's say she got a bonus this year or he lost his bonus this year," Jacobs says. "Next year, there's a really good chance it will revert back."
The study also found that dual-income couples saw a decline in their incomes from 2006 to 2011, albeit a very small one, from $79,206 to $79,100, which could lend credence to Kessler-Harris' theory that the difference has to do with men earning less, not women earning more.
Still, there's good reason to aspire to equal pay: the research showed that the highest median income for dual-earner families occurred when both spouses made similar amounts.
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