The refugee crisis facing Western nations has begun to peak both demographically and politically. The United Nations has reported that more than 6.5 million Syrians have fled to neighboring countries and Europe, and even nations that until recently welcomed refugees are frantically trying to change immigration policy or protect borders. In contrast, as migration has swelled the population in some places, in others, like the Rust Belt of the United States, depopulation undermines future economic development. Some have begun to ask whether population trends can or should determine policy. The answer is yes.

To understand the significance of depopulation in the Rust Belt, imagine that a plague hit the Midwest and four million people had vanished. What would be the economic consequences for the region, its institutions and for individuals? Deindustrialization has operated much like a plague, and just as with a plague, the long term social and economic costs…