There's also an interesting debate in Will's comments over whether social security systems actually depress fertility by encouraging people to free ride on the fertility of others. Contra Will, the evidence for this phenomenon is pretty strong, and also fits pretty well with expected models of human behavior.

But arguing, from this, for natalist policies is depressingly like the social democrats who say, "Well, we need national health insurance, and now that we have national health insurance, we need the state to tell you what to eat and drink so that you won't cost the national health system so much money." The cure for bad incentives from government regulations is not more regulations.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.