The global population grew almost fourfold over the last century. That growth stoked fears of overpopulation, conflict, and ecological collapse. But at some point in the next 70 years, the world population, currently 8 billion, is expected to peak around 10 billion, and then start to decline. An end to humanity’s relentless expansion is in sight.
When it comes, debates about population growth, which have been driven by beliefs that humanity is too fecund for the Earth’s carrying capacity, will acquire a different character.
Why We Wrote This
After a century in which the global population grew almost fourfold, a turning point awaits. This story is the third in a series about falling birthrates. The first looks at why U.S. parents are having fewer children. The second shows how immigrants are powering a population boom in rural Iowa.
Shrinkage is the logical result of tumbling birthrates today, not just in rich democracies like Germany and South Korea, but also in most corners of the planet. “No future currently looks more likely than a long span of global depopulation,” says Dean Spears, an economist and demographer at the University of Texas at Austin.
Depopulation raises complex questions about how best to sustain a flourishing society where institutions can endure. The scale of the demographic transition in the next century or two is one that every country and region will be challenged to imagine and anticipate.
After a century in which the global population grew almost fourfold to 6.2 billion people, stoking fears of overpopulation, conflict, and ecological collapse, a turning point awaits.
At some point in the 2060s, 2070s, or 2080s, the world population, currently 8 billion, will peak around 10 billion, according to forecasts, and then start to decline. An end to humanity’s relentless expansion is in sight.
When it comes, debates about population growth, which have been driven by beliefs that humanity is too fecund for the Earth’s carrying capacity, will acquire a different character. What goes up fast can come down just as fast, measured in decades and centuries, setting the stage for an era of population shrinkage that seems both inexorable and unfathomable.
Why We Wrote This
After a century in which the global population grew almost fourfold, a turning point awaits. This story is the third in a series about falling birthrates. The first looks at why U.S. parents are having fewer children. The second shows how immigrants are powering a population boom in rural Iowa.
Shrinkage is the logical result of tumbling birthrates today, not just in rich democracies like Germany and South Korea but also in most corners of the planet. “No future currently looks more likely than a long span of global depopulation,” says Dean Spears, an economist and demographer at the University of Texas at Austin.
Depopulation raises complex questions about how best to sustain a flourishing society where institutions can endure. Aging societies with declining populations are already a reality in countries like Italy and Japan, where rock-bottom fertility rates have shrunk the workforce and strained public finances. But the scale of the demographic transition in the next century or two, when every country and region would be affected, is far more challenging to imagine or fully anticipate.
Until recently, the United States had avoided what demographers call the fertility trap, in which smaller families beget smaller families. But a sustained drop in birthrates since 2008 and a period of lower net immigration have pushed its population pyramid closer to that of Europe, with fewer young people to support a growing retiree population.
One in 5 Americans will be age 65 or over by 2028, the same proportion as those under age 18, for the first time in U.S. history.
The effects of smaller birth cohorts are already being felt in K-12 schools. Higher education is next in line: The number of college-age students is forecast to peak in 2025 and then decline sharply for several years, putting pressure on smaller, less selective colleges. A study by McKinsey estimated that for colleges and universities not ranked in the top 100, total enrollment could fall by 12% compared with 2012, when large cohorts of millennials filled campuses.
Colleges also braced for an enrollment dip in the 1980s due to smaller high school classes of Gen Xers. But that dip was offset by more women attending college compared with past generations.
To survive the post-2008 baby bust, colleges may need to enroll more underrepresented minority and low-income students, and adjust fees and programming to help students complete degrees without a mountain of debt. Higher education could also be retooled for older students in ways that reflect the demographic shift underway, rather than relying on classes of high school seniors. “There are lots of ways to think about people who enroll in college,” says Sarah Hayford, a sociologist and demographer at Ohio State University.
Sankhadeep Banerjee/NurPhoto/AP
How to address falling fertility rates
What about the economy writ large in a low-birth society? Employers, both private and public, will face pressure in recruiting among a working-age population that is shrinking due to lower birthrates. Filling labor-intensive health and social care jobs will be a priority, given that an aging U.S. population is living longer with chronic conditions, though it’s not living as long as Europeans.
Like most economies, the U.S. relies on a surplus of younger workers whose taxes fund retirees’ pensions and medical care. A declining ratio of working-age adults to dependents, which a slowing birthrate produces, will force governments to raise revenues, reduce Social Security checks, or do both. In its latest demographic forecast, the Social Security Administration noted recent declines in U.S. fertility rates but assumed that births would rebound close to replacement level by midcentury, thus easing the pressure on social-insurance programs.
Most demographers are skeptical of such a rebound, noting that other countries, including European countries that spend far more than the U.S. on family benefits, haven’t managed to reverse similar fertility declines. Without a rebound in birthrates, the U.S. will have far fewer young people entering the workforce when millennials reach retirement age than boomers have had.
Indeed, were it not for a post-pandemic spike in immigration, the current U.S. workforce would already be shrinking due to retirements by older workers. In February, the Congressional Budget Office said that higher-than-forecast net migration would mean more than 5 million additional workers over the next decade, boosting demand and expanding the U.S. economy by 2%.
An attractive destination for migrants, the U.S. could plug gaps in its workforce by admitting more “prime-age” (between ages 25 and 54) foreign workers. This would, in turn, bolster the birthrate as newcomers start families. “People who immigrate to the United States or any other place tend to be of childbearing age,” says Karen Guzzo, a demographer at the University of North Carolina.
But this policy lever, even if politically palatable to U.S. voters, has built-in limitations. Immigrants also grow old and retire. And immigrant families adopt the norms of their new countries. Hispanics used to have larger-than-average families, which reflected the culture of their homelands. Today, most of Latin America has below-replacement birthrates, and Hispanic American women have similar fertility rates to those of native-born women.
The bigger issue is that fertility rates are falling everywhere, even in Africa, which is forecast for the fastest population growth this century. Most of humanity lives in countries where women will bear, on average, between one and two children, a rate that yields an exponential contraction as successive generations become smaller than the last.
Demographic arithmetic is one of exponents: Just as populations expand when adults have multiple children who then go on to have their own large families, the reverse is also true. When two adults have a single child who, together with another “only child,” births just one child, you see the change, a 75% drop – four grandparents, two parents, one child – in just two generations. This is exponential population decline.
Professor Spears is a development economist who studies infant and maternal health in northern India. He notes that smaller family sizes in India match a global trend that spans countries with widely varying societies and economies.
A global baby bust will make it impossible for shrinking countries to import enough workers to replace their own, he says. “Once the birthrate of the world as a whole is below two, we no longer have the easy and valuable answer of welcoming immigrants and instead have to ask the conceptually deeper question of, what sort of human society do we want? Do we want a human society that’s stabilizing? Or a human society that’s depopulating, or something else?”
Vadim Ghirda/AP
Working together and family-friendly policies
Last year, Professor Spears published an opinion piece in The New York Times about the challenges of a depopulating world. He noted that lower fertility meant “tens of billions of lives not lived over the next few centuries.” He said humanity should consider “how to build an abundant future that offers good lives to a stable, large and flourishing future population.”
The online responses from readers were caustic. Most balked at the idea of worrying about future generations and instead bemoaned present-day population pressures.
One reader lamented, “I remember a planet with less than half as many people, and it was wonderful.” Another wrote, “If our diminishing population means some of the damage we’ve caused may slow and even be reversed, then I see that as cause for celebration, not concern.”
Professor Spears says he’s grateful for all the responses to his article, which he has now collected for a future book. “It’s a conversation that’s starting, and that’s good,” he says.
One political response could be investment in pro-natal programs that would, if successful, pay for themselves over the long run. Congress has also taken up bipartisan calls to support an expansion of child tax credits, but demographers say a modest financial benefit to parents won’t do much by itself.
If policy nudges don’t work, could coercion?
In the 20th century, governments intervened to limit family sizes, most notoriously in China, which imposed a one-child policy. Faced with a depopulation tsunami, politicians might restrict reproductive rights for women to boost birthrates. In the U.S., an analysis of the Supreme Court’s 2022 Dobbs decision found that the ruling, which ended the federal right to abortion, led to a 2% bump in births in 13 states with abortion bans, compared with similar states without them.
Critics say reproductive health restrictions would be inhumane and counterproductive in boosting birthrates. (South Korea, the country with the lowest birthrate, banned abortion for more than six decades.) Fiscal incentives, coupled with shared caregiving responsibilities, are more likely to yield extra births than a top-down dictate.
Lyman Stone, a demographer at the Institute for Family Studies, a conservative think tank, says even modest family-support policies “would show up on a long-term population trajectory” and be meaningful for couples struggling with the cost of having children.
As a thought experiment, he points to the slowdown in births among women in their 20s and suggests that society could be reorganized to reverse this trend. Imagine we “give everybody under age 30 a modest universal basic income. Everybody’s going to go to college,” he says.
This would likely incentivize young couples to start having children earlier and more often since their age for a first child strongly predicts a woman’s lifetime fertility. Under this scenario, “your 20s have two purposes: Find a skill and have babies.”
A pro-natal fiscal overhaul would ask older voters to bear much of the cost. That may become harder, though, in democracies with aging societies. In Japan, older voters, who often dictate where scarce resources are spent, increasingly outnumber young voters. Far from redirecting welfare to help support young families, retirees may instead put their priorities first.
Such dilemmas would be less acute if the global decline in birthrates decelerated or stabilized in the decades ahead. The world’s future population size is ultimately unknowable. However much demographic data you feed into models, a degree of humility is necessary, analysts say.
“We didn’t have any reason to expect the [post-1945] baby boom,” says Professor Hayford. “Sociologists and demographers don’t have a perfect handle on what predicts population trends.”
This is the third in a three-part series on falling birthrates in the U.S. and the world. The first in the series, about U.S. parents having fewer children, can be found here. The second, about a county in Iowa where immigrants are powering population growth, is here.