As a general rule, American men earn more than American women. This holds true across industries, across education levels, and across states. But, there's at least one big exception: part-time employees.
In 2012, women who worked less than 40 hours a week generally out-earned men who spent the same amount at their jobs. If they worked 35 hours a week, they earned about 11 percent more. If they worked 25 hours a week, they earned about 4 percent more.
But once females hit that magic 40 hour threshold, their relative pay plummeted, as shown on this graph adapted from a new report by the Bureau of Labor Statistics.
So why do women beat out men while working part-time and lose out while working full-time? My guess is that much (though certainly not all) of the explanation boils down to two reasons: marriage and children. Women, including highly educated professionals, tend to cut their hours once they have families, especially if their husband has a higher salary. Men, meanwhile, are more likely to keep working a full week. And so part-time women, as a group, are somewhat more likely to have gone to college, and far less likely to have dropped out of high school, than part-time men, who may well be working shorter shifts for lack of better options.
The problem for women is that working part-time early in their careers can cost them salary while working full-time later in their careers, thanks to lost experience and perhaps some missed opportunities for promotions. Hence the some of the dropoff at 40 hours. Motherhood might be the most important job in the world. But all too often, our economy still make it into a career killer.
So aside from part-timers, which other women out-earn men? The BLS includes a job-by-job breakdown of the wage gap, and among the nearly 150 occupations with good-enough data to analyze, it found just two where females were better paid: counselors (a category which seems to include everything from school guidance counselors to mental health workers) and "health practitioner support technologist and technicians" (translation: the person who took your x-ray yesterday at the doctor's office). That said, as men look more toward those sorts of traditionally pink-collar jobs for employment, one has to wonder how long that pay advantage will last.