And anyway, the U.S.'s birth rate is still pretty high.

Shannon Stapleton/Reuters

An essay by Jonathan Last published in the Wall Street Journal over the weekend is getting some people talking about fertility. He writes about the United States, "The root cause of most of our problems is our declining fertility rate."

The essay doesn't actually provide any specific problems caused by low fertility. Supporting retired people is the most obvious challenge. But the closest Last comes to describing the actual consequences of low fertility for the U.S. is this, which is based on the experiences of other countries:

Low-fertility societies don't innovate because their incentives for consumption tilt overwhelmingly toward health care. They don't invest aggressively because, with the average age skewing higher, capital shifts to preserving and extending life and then begins drawing down. They cannot sustain social-security programs because they don't have enough workers to pay for the retirees. They cannot project power because they lack the money to pay for defense and the military-age manpower to serve in their armed forces.

I wouldn't put these vague issues at the top of the list of America's problems, but they are worth considering. Rather than try to increase birth rates, I would rather focus on making things work with fewer children, which might have the positive side effect of improving the lives of children. It's a good conversation to have.

But there are three problems with the piece I'll mention:

1. Fertility in the U.S. isn't falling much

The total fertility rate (births per average woman in her lifetime) is about what it was three decades ago. The scary drop over the last several years is apparently due to the recession and looks like it's bottoming out. (In fact, as recently as 2009 I could write, quite reasonably, of the "unmistakable trend" toward higher fertility—look at the increase from 1976 to 2008.)