Everybody knows that women make less money than men. But is that because of discrimination? The lifestyle choices they’re making? Some other factors? A new GAO report offers some new, intriguing answers. 

The study focuses strictly on people who occupy managerial positions. While the pay gap has narrowed slightly over the years, the GAO finds, women in these positions still make approximately 20 percent less than men do: 

By itself, this statistic doesn’t tell us that much. And it doesn’t prove that there is widespread, overt discrimination against women. Women generally work in professions with lower wages and they take time out of the work force to have children. Both factors skew their average pay downward and could plausibly explain a pay gap. (Of course, whether women are in those professions because it’s a choice or because some combination of cultural and financial pressures have forced them into a position is another subject.)

But this is where the GAO survey tells us more than most of the statistical snapshots you read or hear about. (See this Time article for a good rundown of other studies). In looking at female managers' earnings, GAO "adjusted for age, hours worked beyond full time, race and ethnicity, state, veteran status, education, industry sector, citizenship, marital status, and presence of children in the household... [adjusting] for industry sector to control for the possibility that pay differences could occur because female managers tended to be employed in industries that had lower rates of pay." In short, they controlled for almost every factor that could explain the pay gap. And despite all that, they found women made only, on average, 81 cents for every dollar a comparable male made.

The always-fair-minded GAO offered that the gap could be caused by differences in the "level of managerial responsibility, field of study, years of experience, or discriminatory practices." All true. But having controlled for so many other factors, the possibility that at least some discrimination still exists seems far more likely.