Was there ever a time when people were not panicking about population? In 1798, the English economist Thomas Malthus wrote that “the power of population is so superior to the power in the earth to produce subsistence for man, that premature death must in some shape or other visit the human race.” Humanity, then just 1 billion strong, did not fall into the Malthusian trap. Thanks to the Industrial Revolution, it instead underwent a huge expansion in both size and living standards.
More than a century later, when the world population stood at more than 2 billion, the new concern was impending shrinkage. In 1938, Joseph Spengler, an American economist, confidently predicted that “within the next quarter-century true depopulation—a persistent long-run excess of deaths over births—will manifest itself in nearly all the countries of Europe.” By the time Spengler’s deadline had passed, the postwar Baby Boom was in full swing and population concerns had reverted to Malthusianism. In 1968, Paul Ehrlich, a population biologist at Stanford, argued in The Population Bomb that “the battle to feed all of humanity is over” and, regrettably, humanity had lost. In the next two decades, he warned, “hundreds of millions of people will starve to death in spite of any crash programs embarked upon now.” Instead, the world population went from 3.5 billion to more than 5 billion, living standards increased, and child mortality fell.
Today, as humanity numbers just over 8 billion, the concerns have reversed polarity once more. Right around the time of Ehrlich’s doomsday prediction, global fertility rates began a decline that has not stopped. In the United States, Europe, and even India, births are now below the replacement rate of 2.1 per woman. In 2024, South Korea reached a “total fertility rate”—a measure of how many children the average woman will have over her life—of just 0.75, which if held constant would mean that 100 Koreans should expect to have 14 grandchildren and only five great-grandchildren. (The country’s total fertility rate appears to have ticked up slightly since then.) Very few countries outside Africa are above replacement levels. On current trends, the global population may peak in the 2050s at 9 billion, at which point it would start shrinking—for the first time since the bubonic plague of the 14th century.
[Marc Novicoff: Are men to blame for the birth-rate collapse?]
Now the French worry about dénatalité; Hungarians talk about nemzethalál, national death; the Serbs call the baby bust bela kuga, “the white plague.” For prominent figures in the global New Right, depopulation is seen as a threat to civilization. Giorgia Meloni, Italy’s prime minister, has warned that without bold action, her country could be “destined to disappear.” Elon Musk regularly calls low birth rates the greatest threat to civilization. But this population panic may age just as poorly as the prior ones. Even if the fertility decline doesn’t reverse itself anytime soon, the consequences are unlikely to be apocalyptic.
All of these dire projections have relied on a simple mathematical construct: the exponential curve. When you extrapolate an exponential curve with a positive growth rate far out to the future, it ascends toward infinity. One with a negative growth rate descends toward zero. Ehrlich, for example, wrote that if the growth rates of the 1960s continued “for about 900 years, there would be some 60,000,000,000,000,000 people on the face of the earth.” (That’s 60 quadrillion.) Today, long-run predictions look equally dire in the other direction: Newspapers in South Korea warn about “extinction” by 2750; Japan has a running clock, a bit like America’s national-debt counter, ticking down the seconds until the country has only one child left—expected around August 2644.
The problem with these terrifying models is not the mathematics—a population that halves in size every generation will indeed eventually go extinct, just as one that doubles will eventually overrun the planet—but the assumptions. For such projections to be accurate, people would have to resolutely continue to have a certain number of children for centuries, up to the point of planetary exhaustion or human disappearance. They would have to stay the course even as this demographic decline transformed family structures, housing prices, labor markets, and the workings of the welfare state. Yet the experience of the past century, with its baby booms and busts, demonstrates just how dubious that assumption is.
Family sizes seem to change as the world does, in ways that are hard to predict. For the past half a century, in almost every country on Earth, people have been choosing to have fewer children, despite experiencing the best average living standards that our species has enjoyed so far. This synchronized decline confounds many of the baby bust’s potted explanations in American discourse, from both the left and the right. Liberals argue that people are having fewer children because, among other inequities, child care is insufficiently subsidized, parental leave is insufficiently generous, and men do too little housework. But that can’t explain the serious decline in fertility in progressive utopias such as Finland, Norway, and Sweden. Social conservatives blame decaying norms around marriage and family values. Yet even in countries with strong taboos against out-of-wedlock birth and with strong heterosexual-marriage norms, such as India and Turkey, birth rates have also shrunk to below replacement levels.
One of the best predictors of a country’s fertility rate is its human-development index—a composite measure of life expectancy, education, and average income. As societies get richer and better educated, their citizens desire fewer children. And the past century of globalized capitalism has drastically improved living standards everywhere. In 1950, a bare majority of the world’s population lived in extreme poverty, long defined as having an income of less than $1.90 a day. Today, the share who live in extreme poverty is 10 percent, despite the new threshold of $3 a day. Sociologists trying to make sense of demographic trends have theorized that people assured about their material needs start to value their own individuality and self-actualization more than they do having kids. If this is the cause of the fertility collapse, it defies easy correction. It also would explain why all of the policy attempts that advanced countries have made at encouraging more births have generally proved unsuccessful.
Two claims may be true at once: Humanity is not doomed to wither away, but a sharp uptick in fertility does not look imminent. This latter reality raises the question of whether a sustained bout of population shrinkage—even one that eventually reverses—is itself harmful.
Plenty of economists would argue that it is. The essence of “endogenous growth theory,” which earned Paul Romer a Nobel Prize in 2018, is that economies ultimately grow because of ideas, each generated by individuals but then usable by others. In the case of a stagnating population, fewer people are around to have ideas. This is a scenario that the Stanford economist Charles I. Jones has described as the Empty Planet result: Rather than rising exponentially, economic growth stalls out as innovation plateaus. Note that this model predicts not collapsing living standards but rather stagnating living standards sometime in the distant future. Last year, the economists Dean Spears and Michael Geruso, both at the University of Texas, published a book called After the Spike, making an emphatic case for stabilizing the population even if living standards do not decrease, on the grounds that “more good is better.” “I think that life in 2150 is going to be a lot better than life today,” Spears told me recently. But, he argues, it would be better with more people around, because everyone would benefit from the accumulated work in medicine, technology, and even entertainment.
Even so, there will be ways to soften the blow. Economies facing a dearth of new ideas could compensate by devoting greater shares of workers toward such tasks. “If you told me the population would flatline or even fall in half, you could still have as many engineers and people coming up with new ideas as you had before just by drawing more people into that work,” Dietrich Vollrath, an economist at the University of Houston, told me. AI also seems set to increase the pace of discovery, including at the highest echelons of research and development—witness the recent string of pathbreaking mathematical proofs in just the past few months. A recent working paper by economists at MIT and the London Business School argues that “lower birth rates are associated with higher growth in GDP per working-age adult across countries … with no negative impact on aggregate GDP or earnings.” (Emphasis mine.) The paper’s methodology is being actively debated, but perhaps more important than the observed correlation is the authors’ proposed explanation: that when prime-age workers become scarce, companies adapt by developing productivity-boosting technology.
[Read: Americans are in denial about elder care]
This is not to say that the birth-rate decline will be painless. In a paper published this year, David Weil, an economist at Brown University, modeled what life would look like in two possible futures: one in which the U.S. has roughly replacement-level fertility, and another in which fertility is half that. Living standards in the extremely low-birth world, measured by consumption per capita, would be 8.7 percent lower, he calculated. As Detroit and other Rust Belt cities have shown, the problems of shrinkage—the unused school buildings and the underutilized infrastructure—are harder to manage than the problems of growth. When a population has fewer people, businesses have fewer customers available to them and may not even form in the first place—in the same way that the natural audience limit on Hungarian-language podcasts is much smaller than that of English-language ones.
Societies will be dominated more and more by the elderly and remade as a result. Government projections from South Korea anticipate that senior citizens will make up a majority of the country’s population starting in 2045. There are several reasons to think that this graying would be an economic drag. Most successful start-ups are led by people in their 40s, not people in their 60s. There will be intense demand for care, for both physical and cognitive ailments, which is labor-intensive and difficult to do well at scale. Because people are having fewer babies all around the world, the strategy of importing care workers from abroad will become untenable. Governments already spend considerably more on the elderly than on the young, because unwinding entitlement promises is so politically unpalatable. When gerontocracy becomes genuinely majoritarian, this problem will worsen too. Already, there is no available demographic escape route from a crack-up over entitlements. Within the next decade, America’s Social Security trust fund is expected to run out, which would trigger an immediate 22 percent cut in benefits. Even an immediate baby boom the size of Musk’s dreams would do little to alleviate the financial strain, because children generally take time to turn into taxpayers.
Vollrath, the University of Houston economist, views the ongoing baby bust as analogous to such past changes as urbanization and the decline of agriculture. “This is a clear change in preferences,” he said. “It has unintended consequences that are going to drag out for a couple of decades. That may change the growth rate. But ultimately—it’s always interesting to say this as a growth economist—who gives a shit about the growth rate? It’s not actually the thing you’re trying to optimize. You’re trying to optimize welfare and living standards.” From that perspective, he argues, declining fertility is unlikely to be catastrophic. As theories of the future go, this one lacks the apocalyptic oomph of more dire population projections. But it has a more important virtue as a prediction: It may be what actually happens.
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