My Selfish Reasons to Have More Kids tries to persuade people to increase their fertility.  Jonathan Last’s What To Expect When No One’s Expecting explicitly disavows this aim:

Finally, this
book is not an attempt to convince you to have babies.  Children are
wonderful, in their way.  But you’ll find no sentimentalizing about them
here.  To raise a child is to submit to a staggering amount of work,
much of which is deeply unpleasant.  It would be crazy to have children
if they weren’t so damned important.

If this is true, though, why did fertility stay high until the modern era?  Last points an accusing finger at government retirement programs.  Before the 1930s…

children made good financial sense.  You invested your resources in
raising them so that they would be able to provide for you when you
could no longer work.  Beginning with the New Deal, the logistics of
this social compact began to change.


In a
world in which childbearing had no practical benefit – the government
will care for you if you don’t have children to do so – then parenthood
becomes a simple act of consumption.  People have babies because they
want to, seeing it as either an act of self-fulfillment or as some kind
of moral imperative.

There’s one big problem with this story: Contrary to popular opinion, children have never been a remunerative retirement plan.  In pre-modern times, people rarely lived long enough to collect their “pension.”  This has been verified by anthropologists and economic historians alike; see Ted Bergstrom’s excellent review in the JEL.  Long before the birth of the welfare state, buying land and money-lending (and even hiding money under your mattress!) made far more financial sense than having kids.

Indeed, as I argue in Selfish Reasons to Have More Kids, kids are a better deal in modern societies than in traditional societies.  In purely financial terms, they’re still a money pit.  But at least nowadays you’ll probably live long enough to collect two or three decades of non-financial assistance and companionship.

The deeper problem with Last’s story, though, is that he doesn’t appreciate the weirdness of declining fertility.  In his eyes, what we’ve seen all makes sense:

A man born into a capitalist system… has to fend for himself and create himself… The man with a family has more obligations, which means less freedom to move and take risks.  In this way, having a family is in a very real sense never in someone’s self-interest… In time, as women began to work in serious numbers in the twentieth century, they, too, became individuals who had to keep moving – so today we have two self-interested individuals, and they both know it’s not to their advantage to start a family.  It might not even be to their advantage to commit to marriage at all.

I’d say “so what do they do?” but we already know what they do.  They stop having children and they stop getting married.

If you’re familiar with evolutionary psychology, the preceding story should baffle you.  Evolution doesn’t select for creatures that maximize their individual interest; it selects for creatures that maximize their genetic interest.  We should expect our demand for procreation to be as resilient as our demand for food.  Indeed, given a basic grasp of evolutionary psychology, you’d expect humans to respond to prosperity by breeding like rabbits.

You could object, admittedly, that evolution made us desire sex, not children – and point to contraception as the key innovation.  But non-reproductive sex became available as soon as cavemen figured out where babies come from.  Contraceptive technology has expanded our options, but the effect on fertility is far less clear than people think.  Yes, fertility fell after the introduction of the Pill.  But fertility went way up soon after the U.S. government issued condoms to a whole generation of men during World War II.   Returning G.I.’s had the technology to make a Birth Dearth, but they and their wives chose a Baby Boom instead.

My point, of course, is not “the facts of fertility clash with the theory of evolution, so the facts have to go.”  My point, rather, is that Last’s story has major plot holes.  Instead of saying, “Of course fertility is declining,” he should be asking, “Why on earth is fertility declining?!”  The answer is anything but obvious.