We would really like to know the answer to this question: is the gender pay gap something that is done to women by an uncaring patriarchy or is it something done by women? That is, are we imposing something upon women or is that undoubted pay gap a result of female choices? Voluntary Exchange has made a very clever catch here (and managed the almost unbelievable, found something useful in the writings of Beatrix Campbell) to aid us in answering the question:
Let me make sure I get this right. When women have less freedom to choose their jobs, earnings were equal, but when there is a policy shift that allows women more freedom to choose their jobs their relative earnings fall. Folks … this is prima facie evidence that the gender gap in earnings is caused by women’s choices and not by social restrictions.
We have, as all will recall, been shouting here for some years now that there isn't actually a gender pay gap at all. There's a motherhood pay gap instead. And as this example shows it's about the choices that women make over children and child care that create it. This must be so: if an increase in economic freedom leads to an increase in the pay gap then it must be the choices that people are making with that new found freedom that is causing said gap.
The pay gap is emergent from the choices of women. QED.