Feminists have long debated the veracity of the “opt-out revolution” meme, but a forthcoming study from the Federal Reserve Bank of New York (described by Reuters) does in fact find college-educated women whose spouses are similarly educated dropping out of the workforce. The study shows a drop in these women’s workforce participation of .1 percent a year between 1993 and 2006, in contrast to growth in their ranks of 2.4 percent between 1976 and 1992.

This trend seems to be heavily influenced by the pay gap. In 1975, the pay for men and women who graduated from college was about even: they both made 43 percent more than non–college graduates. But by 2008 male grads were making 92 percent more, while women were making 70 percent more, a gap of 22 percentage points between them. In fact, as Amanda Hess recently pointed out, at every level of education beyond high school, women experience a shortfall in comparison to their male peers. Overall, men with post–high school education make over $800 more per month than women with the same level of education. The gap only gets worse the more education they take on: for example, men with a bachelor’s degree in business make $1,000 more each month, and men with advanced degrees in business make $1,400.

This should throw some cold water on all of the excitement around the fact that women are getting more college degrees than men. There have been a lot of predictions that women’s gains in higher ed will give them a huge edge in the future economy. But if they are shelling out tuition or taking on loads of debt to end up making less than men, and then dropping out of the workforce altogether, the idea that their education levels will mean economic dominance evaporates.

Surprisingly, one of the study’s authors, Stefania Albanesi, warns that this may not be due to the tug of caring for children. As she told Reuters, “These women usually give up their jobs when their children are school-age and not babies any more.” Childcare duties don’t end when school begins, though. With workers being made to log longer hours, afterschool care is still likely to be an issue. As Monika Bauerlein and Clara Jeffrey reported last year, on average Americans work 122 more hours a year than the British and 378 more than Germans.

And salary differences between husband and wife can be the deciding factor in who drops out of a job to care for children. As Linda Hirshman wrote a few years ago, “The economic temptation is to assign the cost of child care to the woman’s income.” If what a woman makes in a year is dwarfed in comparison to what it costs to hire a nanny, many couples decide that it makes sense for her to stay home, without combining both incomes and seeing whether they have room to hire help.

This phenomenon happened to a woman I interviewed who was about to have a baby. Deborah Sprzeuzkouski was pregnant, living a middle-class life in New York City, and struggling to figure out how she and her husband were going to afford childcare. “We’re just going to have to watch our budget and live the same way we’ll live during my maternity leave, which is on one salary,” she told me. “Because the way I’m looking at it, my salary goes to daycare.”

The recession seems to have temporarily halted this trend, as spouses often returned to the workforce when job losses hit their households or their incomes fell. But it may have picked up again now that we’re seeing some better economic signs: the number of working-age women working or job seeking was down .6 percent in 2010 from the year before. This may be coinciding to some extent with reduced childcare support at the state level. The National Women’s Law Center reported that thirty-seven states pulled back on various forms of assistance in 2011, and on top of this families are worse off now than a decade ago. This may not be the only cause, but we’re not making it any easier for women to stay in the workforce who make less money than their husbands and are also the default caretakers.