Fertility Decisions and the Gender Gap

by F.

A new NBER paper entitled Does Science Promote Women? Evidence from Academia 1973-2001 by Donna K. Ginther and Shulamit Kahn ought to provoke an interesting discussion. Here’s the abstract:

Many studies have shown that women are under-represented in tenured ranks in the sciences.

Right, right. So what was the hypothesis?

We evaluate whether gender differences in the likelihood of obtaining a tenure track job, promotion to tenure, and promotion to full professor explain these facts using the 1973-2001 Survey of Doctorate Recipients. We find that women are less likely to take tenure track positions in science,

OK. But here’s the twist:

the gender gap is entirely explained by fertility decisions.

This shouldn’t be that surprising, but it will shock some because the discussion about achievement differences between men and women in science has gotten sidetracked by talk of innate differences. Forget that:

We find that in science overall, there is no gender difference in promotion to tenure or full professor after controlling for demographic, family, employer and productivity covariates and that in many cases, there is no gender difference in promotion to tenure or full professor even without controlling for covariates. However, family characteristics have different impacts on women’s and men’s promotion probabilities. Single women do better at each stage than single men, although this might be due to selection.

How come? Simple:

Children make it less likely that women in science will advance up the academic job ladder beyond their early post-doctorate years, while both marriage and children increase men’s likelihood of advancing.

Tyler Cowen notes this result is “politically incorrect.” Matt Yglesius doesn’t see why. Here’s why: this could also explain the male-female wage differential. If so, women are choosing children over pay, which means there may not be a gender gap in any interesting sense—there are just different choices being made. You want to have a baby? Fine. You’ll get less money. Still want to do it?

This result, to me, is not that surprising. My wife and I are both lawyers and we’ve seen numerous women attorneys take maternity leaves and then not come back to the practice of law. This makes firms reluctant to hire women in the first place—Why train someone if they aren’t coming back? “Someone else can subsidize childbearing,” is how they reason. The stock of women attorneys thus shrinks, so it’s not surprising that fewer end up in the top-tier. Law is an interesting case because no one could say with a straight face that women are less “legally gifted” than men (the analogue of “women can’t do math” in the sciences). Some of the best lawyers I know are women.

Many professional women, of course, do come back to practice. But they generally have a very hard time, not just because they have taken a few months off, but because once they come back they must breast feed, worry about childcare (let’s face it: the burden falls on the woman most of the time), and sleep, like, 30 minutes a night (which tends to decrease job performance). The Frontal Cortex thinks maternity leave is the answer, but probably not: the “problem” (read: the kid) doesn’t go away once women come back to work, though it can be alleviated by a full-time nanny, or helpful relatives. Working mothers, at whatever level, have a tough time, as most of us have noticed.

Should we try to correct the achievement gap if it is the result of voluntary choice? It’s hard to see why. If I take a few years off from my job and, say, play tuba in a touring polka band, then come back to work, I will probably not catch up with my peers. Should I be given a helping hand? Only if we want to subsidize polka bands. Do we? I don’t see why. So the politically incorrect part of this paper is this: it focuses us on whether we want to subsidize childbearing. And that is a hard question. I don’t know the answer.

The full version of the NBER paper is here.