A working paper from the University of Chicago asserts that much of the gendered earnings gap comes down to what women major in and what jobs they choose to take after graduation, but it noted that over the past few decades, there have been more women entering higher-paying majors and, therefore, higher-paying professions. 

The study defined a major’s potential wage based on the "median log hourly wage of native, white men aged 43-57 who matriculated with that major." With this measure, it compared the major choice of women relative to the major choice of men for each birth cohort where the units of the index are in potential log wage differentials. It found that, across all birth cohorts, women systematically choose majors with lower potential wages relative to men. It also asserts that, on top of this, even when women do graduate with high-paying majors, they tend to go into lower-paying jobs anyway, and tend to select jobs with fewer hours. 

However the study has pointed to change over time. The researchers determined that college-educated women born in the 1950s matriculated with majors that had potential wages 12 percent lower than men from their cohort. In contrast, for college-educated women in the 1990s, that gap is now about 9 percent. The researchers attributed this to women beginning to select higher-paying majors and professions.