Robin explains a new theory of falling fertility that he cooked up with Bill Dickens on the road back from GenCon:

The key idea: farming pressures strengthened a fem forager tendency
to, when personally richer, invest more energy in pursuing status,
relative to raising kids. So when all fems are rich, they all invest
more in status, relative to kids, and fertility falls

Robin then explains the theory in great detail.  But unless I’m deeply misunderstanding it, this “excellent” theory doesn’t even get off the ground.  Like Feyrer and Sacerdote’s theory, Dickens-Hanson implies gender conflict: In the modern world, men should want more children than women, and this gap should get larger as people get richer.  But in reality, men and women around the world see eye-to-eye on this question – see the World Values Survey, question D017.

But doesn’t the Dickens-Hanson mechanisms work for men, too?  Robin thinks it does, but admits that it doesn’t work as strongly:

Much of this analysis also applies to men… [M]en today may also devote
excess effort to developing status markers. The main differences seem
to be that 1) men tend less to directly raise kids, 2) men can father
kids at older ages, and 3) men gain more reproduction from being high
status.  So men should work even harder to gain status markers. But
even so, raising overt kids will less distract men from pursuing high
status, and a man’s delay in starting kids will less reduce his
fertility.  Thus excess male status efforts probably do less to reduce
overall fertility.

Do I have a better story of declining fertility?  Not one that’s methodologically acceptable to Robin.  But there’s one thing I do know – any theory that implies serious gender conflict is wrong.