MBD notes some of the practical reasons for doubting immigration as a solution to the problems caused by declining birth rates. But there’s another issue: Americans say they want to have more kids than they end up having. To the extent that public policy is the source of some of the obstacles to their achieving goals they deem important, it makes sense to try to eliminate those obstacles. It may even make sense to consider some policies that facilitate their achieving these goals — as we do when it comes to many other goods that people seek.

If the problem we’re focusing on is the gap between stated and achieved desires for family size, more immigration can’t possibly be the solution.