Overall births have since bottomed out, but much of the increase was older women who had clearly been putting it off for economic reasons. Ultimately a secular decline in the U.S. birthrate seems extremely likely. Right now it’s sitting at 1.87, and I’d bet that it will eventually land somewhere around Germany’s 1.38 within a decade or two. The reason is that without paid leave and other benefits, having children is a terrific pain in the neck even for rich people.

You might be thinking: Well, that doesn’t sound so bad. There are “too many people” in America anyway, and population growth is a serious strain on resources. That’s true up to a point, but as I’ve argued before, when it comes to rich nations whose birthrate is already pretty low, the efficiency of a society matters much, much more than the absolute number of people. French carbon dioxide pollution per person is less than one-third that that of the U.S. — meaning that equaling their emissions would have a greater effect on climate change than cutting the population in half.

What’s more, a sharp collapse in the birthrate of a society means enormous political strain. The retired, non-working share of the population will grow, and the share of workers supporting those retirees will shrink. In theory, so long as productivity growth is chugging along, it should be possible to thread that needle and give more to workers and retired people, but in practice it will mean more fighting between creditors and debtors, as can be seen in Japan. (It’s also worth noting that U.S. productivity growth has been terrible of late.)