Researchers often control for certain variables if they suspect that those variables might be exaggerating the size of an effect. In the case of the pay gap, economists often adjust their data to compensate for the fact that, for example, men are overrepresented in high-paying computer programming jobs, and women are overrepresented in low-paying service jobs. These adjustments lead to numbers that stand as good estimates of how big a pay gap would be if men and women were represented in equal numbers in each profession. There are usually other variables that researchers control for, too; geography, experience, and job titles are other variables with known effects, so filtering them out from the numbers is a step toward isolating the effects of gender on pay.

But the striking thing is that even after adjusting for so many factors, there’s still a statistically significant pay gap. (Pay-gap skeptics often note that the gap shrinks after taking these factors into account, but it’s supposed to—those statistical adjustments were intended to create a more definitive, standardized measurement.) The fact that a gap remains at all after such adjustments shows that the problem defies any simple explanation. As Robert Hohman, the CEO of Glassdoor, wrote a few months ago in Fortune:

Factoring differences in education, experience, age, location, job title, industry and even company, our latest research reveals that the “adjusted” gender pay gap in the U.S. amounts to women earning about 94.6 cents per dollar compared to men. It is remarkable that a significant gap persists even after comparing male-female worker pay at the job title and company level.

That 5-cent difference is evidence that something isn’t getting accounted for in all those variables that economists are adjusting.

The premise of the occupational-differences argument is that if women are choosing jobs that are easier to do, they shouldn’t be paid the same wages as men. But what that argument—that women are to blame for keeping their wages down because they’re choosing bad jobs—doesn’t take into account are the many things that contribute to the way men and women choose their careers.

Gould, along with her co-author, Jessica Schieder, argue that the decisions women make regarding their careers do not happen in a vacuum: These are decisions shaped by cultural norms and expectations, societal forces that aren’t cleanly captured by pay data. Gould and Schieder point to a multitude of messages that women get from society about what sorts of jobs they should pick: The expectations of American mothers could lead women to take lower-paying jobs because they’re more likely to offer flexible (or shorter hours), while fears of discrimination might steer them away from higher-paying professions. In other words, adjusted statistics could be missing the role of discrimination in the processes that lead women to choose the careers they do.