Why is there a gender pay gap among senior managers? It's tempting to blame evil patriarchal capitalists. But there's more to it than this.
There's good evidence that women are - on average - less aggressive negotiators than men, and so prone to get worse deals. Women are also less overconfident and so less likely to get top management jobs. And they are also less likely (pdf) to want to enter into the sort of high-stakes competitions that allocate top jobs.
But why do these differences exist? A neat experiment sheds light.
Economists got some MBA students to do some mental arithmetic, being paid according to the number of sums they got right. They were offered a choice of payment methods. They could either be paid simply according to the number they got right, or they could be paid much more, but only if they got more answers correct than three rivals. So they could choose between piecework and competition.
Before they were given this choice, the subjects were asked to fill in a questionnaire. One group was given a questionnaire about their career, the other about family and gender issues.
And here's the thing. Among those given the career questionnaire, men and women were equally likely to chose the competition - a quarter did so. However, when given the gender questionnaire, 37% of men chose competition, but only 7% of women did so.
This suggests that an aversion to competition among women is not some biological given, but is instead a product of their social identity. And a very simple reminder of this identity induces women to shy away from competition, and men to seek it. This is consistent with research by Uri Gneezy and colleagues, which has shown that, in a matrilineal society, it is women (pdf) rather than men who choose to compete. It's also consistent with George Akerlof's and Rachel Kranton's under-rated book, Identity Economics, which shows how our identities and the social norms attached to them shape our economic behaviour.
And it's also consistent with the feminist claim that gender is, at least in part, a social construct.