The Daily Caller which published a story about this study Monday evening. A pair of researchers at Harvard, one of whom is listed as a Ph.D. candidate in the field of economics, has published a working paper which examines the gender wage gap. In order to determine why men seem to make more money than women at the same job, the authors looked at Massachusetts Bay Transportation Authority data on bus and train operators doing the same jobs under the same union contract. What they found is that the wage gap that exists is the result of men being more likely to work overtime while women are more likely to prioritize time at home. From the study’s conclusion:

We show that a gender earnings gap can exist even in a controlled environment where work tasks are similar, wages are identical, and tenure dictates promotions. The gap of $0.89 in our setting, which is 60% of the earnings gap across the United States, can be explained entirely by the fact that, while having the same choice sets in the workplace, women and men make different choices. Women use the Family Medical Leave Act (FMLA) to take more unpaid time off than men and they work fewer overtime hours at 1.5 times the wage rate. At the root of these different choices is the fact that women value time and flexibility more than men. Men and women choose to work similar hours of overtime when it is scheduled a quarter in advance, but men work nearly twice as many overtime hours than women when they are scheduled the day before. Using W-4 filings to ascertain marital status and the presence of dependents, we show that women with dependents – especially single women – value time away from work more than men with dependents.

You might be thinking that men are more likely to take overtime because they are less likely to have children at home to care for. However, the researchers were able to control for this as well, comparing single dads with single moms. The result? Single men with dependents were much more likely to accept overtime:

Regardless of whether or not they have dependents, men are 4 to 6 percentage points more likely than women to accept an overtime opportunity. The difference in acceptance rates between men and women is higher, though, if the operators have dependents, especially so if the unscheduled overtime is offered on a weekend or on a day when the operators are already scheduled to work. The presence of dependents makes the overtime opportunity more valuable for men and time spent outside of work more valuable for women…

Diving deeper still, Figure 9 reveals that the biggest gaps in acceptance rates (up to 8 percentage points) are between single women and single men with dependents. These results
suggest that single men are able to take care of their dependents by working more overtime, possibly to pay for child support or to finance other forms of child care. Single women, on the other hand, appear to be making the decision to do the caretaking themselves rather than to caretake through additional earnings. It is, of course, possible that for women this situation is not as much a personal preference as it is a constraint. Thus, our results imply that differences in care-taking approaches and responsibilities appear to be a major reason why women work less overtime than men.

Here’s Figure 9:

And if you look at married men vs. married women, the gap in accepting overtime nearly disappears:

Crucially, a gap in overtime acceptance rates barely exists for those who are married. As we can see in Figure 10, married male operators with dependents are only 0 to 2 percentage points more likely to accept overtime than married women with dependents. This suggests that those who are married with dependents, men and women, are able to divide up caretaking responsibilities at home in a way that allows them to work overtime at similar levels. Or, perhaps, the presence of dependents necessitates that women, as much as men, earn as much as possible to afford care.

This isn’t the first time someone has argued that the gender pay gap is the result of different choices made by men and women, but in this case, with the men and women working the same jobs under the same contract it’s hard to explain the differences away as the result of some other hidden factor.

I suppose some feminists will argue the desire by women to spend more time at home rather than working overtime is culturally conditioned. Maybe they even have a point. Still, ‘women are making the wrong choices at work’ is a very different argument than ‘women are systematically being held back at work.’