Let's save the human species!

Take a look at the marvel that is modern China. The endless gleaming lines of bullet trains. The air taxis and the drone delivery services and the driverless cars. The bubble tea franchises and the cavernous malls and the fast fashion and the pay-with-your-face apps and the robot waiters and the automated factories. The Shanghai clubs and the side streets of Chongqing and the manicured parks of Shenzhen.

You are looking at the peak. China will continue to be a spectacular, world-leading civilization for a couple more decades, but sometime around the century’s halfway point, demographic decline will begin to sap its vitality. Sometime around the mid-2010s, China’s birth rate fell off a cliff, and has not stopped falling since:

It’s difficult to state just how stark and catastrophic of a collapse this is. The number of births in China fell by 17% in just the last year. In fact, as economist Jesús Fernández-Villaverde recently pointed out, China had fewer births in 2025 than in 1776, when its population was less than a fifth of what it is now.

China’s total fertility rate now stands at around 0.93, less than half the replacement level. At that rate, every four grandparents will have fewer than one grandchild. Fernández-Villaverde explains what this means for the future of China’s population:

[I]f China could somehow sustain 7.92 million births per year from now on, its population would eventually stabilize at roughly 625 million, far below today’s 1.405 billion. In reality, as smaller cohorts reach childbearing age, births will fall well below 7.92 million. Hence, 625 million is a very generous upper bound[.]

But this isn’t a post about China; it’s about the whole world. Those who expect China’s low fertility to end its bid to dominate the globe are in for a severe disappointment, since fertility is falling in the rest of the world as well. It’s true that China is an especially severe case — a TFR of less than 1.0 puts it in a special category with Korea, Taiwan, Singapore, and Thailand (Japan, interestingly, is still slightly higher). But over the past decade, fertility has begun collapsing all over the world, much faster than it had been declining before.

Fernández-Villaverde has a good set of slides from 2023 explaining why the new fertility crisis is different and more urgent than traditional concerns. In earlier times, fertility tended to gently decline in each country until it was just under the replacement rate — the kind of baby deficit that seemed like it could be fixed with reasonable policies. But since the mid-2010s, the fertility decline has accelerated, and there seems to be no bottom to the new collapse; every year, statistical agencies revise their already negative projections downward even more.

When they confront these stark numbers, there are several things that people tell themselves (or shout on social media) to try to cope with the notion of a shrinking humanity. I’ll go through the most common of these coping statements, and explain why each of them is wrong.

1. “The only thing that matters is per capita living standards, so a shrinking population is fine”

People who say this forget that a shrinking population is also an aging population. Old people can work longer, but eventually their bodies and minds break down and they need to be supported by younger workers. Here’s what I wrote in 2024:

[With an aging population] every working-age adult has to toil harder and consume less in order to support a growing number of people who are too old to work…In the 1990s and 2000s, there were more than 5 working-age Americans (age 15-64) for every elderly American (64+). By 2021, there were fewer than 4. That means that the economic burden of supporting each elderly American is now shared among only 4 people instead of 5…And in other rich countries, it’s even worse. In France, there are only 3 working-age people for every elderly person. In Japan, there are only two[.]

And here’s what I wrote in 2023:

[A] shrinking population means that profitable investments will be a lot harder to come by…[I]f there are more old people and fewer younger people, then demand for the assets of the old is going to have to be split among more sellers. And that will mean a lower price. In other words…people will have to save more and more during their working years in order to make it to a comfortable retirement.

And here’s the upshot:

So in general, the shrinking world will be a world of toil. Working people will have to bear the burdens of higher taxes, more eldercare, and longer working lives. And despite working more, they will have to be thrifty and ascetic, saving more money for their own retirements.

On top of all this, a shrinking population creates a problem for physical infrastructure. Road systems, sewer systems, electrical grids, and so on were built to support a certain size of population; cut the population in half, and there won’t be enough people to support all that infrastructure in any given area. We tend to forget just how quickly human structures