ON THE LEFT and the right, in Europe and the United States, a consensus is growing: People aren’t having enough kids—not enough to support the welfare state, not enough to preserve the culture, not enough to keep advanced economies young, thriving, and entrepreneurial. The last time the U.S. was at replacement level fertility (the number of kids the average woman must have to stave off population decline, without immigration) was 2007. Replacement level fertility is roughly 2.1 kids per woman. Since then, America’s total fertility rate dropped to 1.66. This, in turn, led to a lot of unanswered questions about the fate of federal entitlement programs, innovation, education, politics, and culture in an aging country.
To many, the solution is obvious: Americans should have more children. Yet pro-natalist policies have…