Matt Yglesias finds something to like and something to dislike in Ross Douthat’s recent column. Douthat observes that a robust birthrate is among America’s greatest economic advantages and bemoans its recent stagnation. He proposes polices that make it easier and cheaper to raise more kids. At the same time, Douthat acknowledges the limits of politics in achieving that goal:

Beneath these policy debates, though, lie cultural forces that no legislator can really hope to change. The retreat from child rearing is, at some level, a symptom of late-modern exhaustion — a decadence that first arose in the West but now haunts rich societies around the globe. It’s a spirit that privileges the present over the future, chooses stagnation over innovation, prefers what already exists over what might be. It embraces the comforts and pleasures of modernity, while shrugging off the basic sacrifices that built our civilization in the first place.

Yglesias agrees with Douthat’s government-friendly prescription, but rejects his conservative diagnosis. According to Yglesias:

It’d be a much better country if social conservatives would stop writing things like that second paragraph and focus instead on [the policy proposals] in the first paragraph. France and Sweden, rather sensibly, have decided that the continued existence of French and Swedish society are matters of public importance and that this offers a particular reason to invest funds in supporting middle class families. In Sweden, for example, about 0.8 percent of GDP is spent on subsidized parental leave. That’s be the equivalent of a $120 billion a year program in the United States. But I think it would be money well spent. The French government’s level of investment in bolstering the welfare of newborn babies and new mothers is the stuff of legend and fiscal cost aside sometimes veers into the weird, but again these policy levers—more than condemning the “decadence” of people responding to the situation that actually exists—are how you give appropriate weight to the importance of childrearing without trying to micromanage people’s lives.

Yglesias’ objection is both typical and telling. It’s typical because it reflects the neo-liberal assumption that economic incentives are the major determinant of behavior. It’s telling because it ignores evidence that this just isn’t true.

Yglesias is right about the subsidies that France and Sweden lavish on middle-class families. But he doesn’t mention evidence that, by themselves, they haven’t had dramatic success in promoting fertility.

According to UN statistics, France averaged 1.89 births per woman between 2005 and 2010. That’s below the rate necessary for replacement and 137th in the world. Sweden averaged 1.8 births per woman. That was good for 151st place. Both figures are somewhat better than other prosperous European countries, such as Germany. But they’re well below the United States, which had a fertility rate of 2.05 births per woman during this period.

Projections for 2012 suggest that France’s fertility rate may improve considerably to 2.08 births per woman. Sweden’s fertility rate, on the other hand, is projected to drop to 1.67. Fertility in the United States on other hand, is expected to remain essentially flat.

These numbers suggest that changing incentives is insufficient to promote larger families.      Fertility in France and Sweden might be even lower without generous subsidies. Yet those policies haven’t exactly created a baby boom. And Americans continue to reproduce at a relatively high rate even in the absence of generous social policy.

Although it may not be politically helpful to say so, Douthat is mostly right about the underlying reason for these trends. Quite apart from economic incentives, the sexual revolution fundamentally altered the normative order of Western societies.

But Douthat’s wrong to give present comfort such a dominant role in this structure. The master value of the modern West isn’t enjoyment, but personal autonomy. And it’s hard to pursue your own goals in your own way when encumbered by offspring, particularly in the numbers necessary to population growth.

If they are to have even limited success, then, policies intended to remedy declining birthrates must accept this change. In other words, they can and should aim to make it easier for people who want families to have and raise children.

But there’s not much government can do to encourage people who regard children as a burden to produce them. Only a major cultural change could do that. In this respect, the demographic future of Western societies may depend on the fate of their religious traditions much more than on their tax codes. I’m not holding my breath for neo-liberals to acknowledge that.