What could finally close the gender pay gap?

The gender pay gap may be one of the most enduring problems of America's labor market.

Women now make about 79 cents for every $1 men earn, which is the smallest wage difference between the genders since 1960, according to U.S. Census Bureau. But before women and their supporters start planning a celebration, here's a sober caveat: Progress is at a standstill.

The 1980s was a good decade for shrinking this gap, but since then improvement has been "slower and more uneven," with a number of trends such as the women's labor force participation rate stalling out since the 1990s, according to a recent paper from Cornell University economists Francine D. Blau and Lawrence M. Kahn. The fact is, how Americans work and view gender may need a radical overhaul to get the pay gap to narrow any further.

That's because several stubborn issues continue to hamper women in the workplace. Some of the pay gap can be explained by factors such as occupational choice and education levels, and economists are increasingly pointing to gender discrimination and a lack of public policies to support working parents as serious issues. Together, these factors mean creating a level playing field isn't as easy as it seems.

For instance, women are now more likely to have college degrees than men, but men continue to dominate so-called STEM fields (science, technology, engineering and mathematics), which tend to pay more than other jobs. Yet the math scores of high school girls and boys have narrowed, leading some researchers to investigate whether educational policies and other factors are pushing more boys into STEM fields, the Cornell researchers noted.

And some jobs remain male-dominated -- and tend to pay higher wages, such as CEOs -- while lower-paying fields such as education are still largely the province of women. Pay for jobs such as teaching and caregiving "do not fully reflect the social value they provide," according to a report published this month by Third Way, a research group that espouses a centrist viewpoint.

So, why don't women just move into higher-paid male fields? In many cases, they're doing just that. Take veterinary science. Decades ago, it was a man's occupation, but now male veterinary students are in the minority.

Yet a not-so-funny thing happens when women are on the way to a higher-paid field: Its wages decline, according to a 2009 paper from researchers at New York University, University of Pennsylvania and the University of Haifa. That reflects a devaluation of work women do, regardless of their occupation.

That may suggest employers either don't value the work women produce as highly as they do men's work, or that they're making assumptions about women's tenure in the workforce, such as a woman might leave to start a family.

Many experiments have illustrated that employers discriminate against women, such as one 2012 study that asked science faculty at six large universities to rate the application materials of male and female applicants. The trick was that they were identical for both genders. Despite this, the faculty rated the male applicants higher and also gave them a salary that was $4,000 more than the female applicants, according to the Cornell paper.

Bias and similar issues are called "unexplained" reasons, in that they can't be tracked by economic measures or other yardsticks. Interestingly, these unexplained issues appear to be most stubborn at higher income levels, which suggests that highly skilled women are hitting a "glass ceiling," according to the Cornell researchers.

Highly educated women might be making choices to take a backseat to their husband's career, choosing to take a more flexible job (with lower pay) so that their husband can pursue his career. That points to the need for policy issues that support families -- and not just women.

Paternity leave is strongly correlated with the number of women in corporate board seats, for instance, according to a study published earlier this year from The Peterson Institute for International Economics. That's because such policies help shift child care demands more equitably between men and woman, while a company with only maternity leave may be shifting that work only onto women.

"Ending the gender pay gap will require a multi-pronged approach with policy solutions targeted at multiple problems with laser-like precision," Third Way said in its report. "Just as there is no single number to fully represent the pay gap, there is no single fix. Achieving gender pay parity will require both determination and creativity among policymakers, employers, workers, and educators alike."