Half a century ago, biologist Paul R. Ehrlich became a household name for going on The Tonight Show with Johnny Carson and predicting demographic doom. Women worldwide were having five or more children on average, Ehrlich noted, and most of those offspring were surviving to have their own babies. At this pace, he warned, “mankind will breed itself into oblivion.” And so, demographic determinism took off with a vigor not seen since the days of Thomas Malthus in the late 18th century.
Ehrlich’s best-selling book, The Population Bomb (1968), which he had gone on television to promote, began in the Indian capital of New Delhi. Ehrlich described a late-night taxi ride with his wife and daughter. “The streets seemed alive with people,” he wrote with ill-disguised disgust. “People eating, people washing, people sleeping. People visiting, arguing and screaming. People . . . begging . . . defecating . . . clinging to buses . . . herding animals.”
Off the street, they were also having kids. India’s population, Ehrlich warned, could double in a generation. He was correct. India’s population—and the world’s—did hit that mark between 1968, when the book was published, and the close of the 20th century. But the mass starvation he foresaw never happened. Instead, it was headed off by a green revolution in plant breeding that increased food production around the world by at least as much in the same time frame.
Technology had broken the chains of what seemed like a terrible demographic destiny, just as the Industrial Revolution forestalled Malthus’s predictions in Europe. Today, even as India’s citizenry has well surpassed Ehrlich’s prediction, the country exports rice most years. And rather than continuing to grow unabated, the population is set to plateau and perhaps even decline in decades to come. In November 2021, the country announced that its fertility rate has dropped from 5.9 to 2.0, below the long-term “replacement level” of 2.1 children per child-bearer. Several regions have lower still fertility rates of 1.6 or even lower.
So food is up and fertility is down. Problem solved?
Despite the plunge, it will be a while before India’s population peaks. Two-thirds of Indians are under 35 years old. So even with below-replacement fertility, there are enough people having children to push up overall numbers for another 40 years or so. Indeed, India will probably overtake China as the world’s most populous nation in 2023 or 2024. But before the centenary of Ehrlich’s apocalyptic warnings, the country will almost certainly go from baby boom to bust.
In that, it won’t be alone. As of 2021, only two of the world’s ten most populous nations still have fertility rates above 2.1: Pakistan and Nigeria. The rest, including China, the United States, Russia, Brazil, Mexico, and most recently Bangladesh and Indonesia, are at or below replacement fertility levels, meaning that they too will see declining populations by mid-century.
Nothing is certain, of course. Fertility rates can go up as well as down, but the trend toward radically smaller families is well established around the world, whatever the local culture, religion, or economic circumstances. Even in China, where fertility was artificially suppressed for 35 years due to the country’s coercive one-child policy, the rate has remained stickily low even after that policy was jettisoned in January 2016.
The population bomb is thus being defused, mostly as childbearing people around the world take charge of their own reproduction. From the days when the global population doubled in a generation, threatening to eat up all the resources on the planet, the world is now unlikely to see a repeat. The world’s Ehrlichs might see cause for celebration. But not so fast: population decline could come with its own bombshells.
The heirs to Ehrlich’s catastrophism still fret that, as the number of people continues to rise (even if only temporarily), the environment could yet collapse. The latest projection from the United Nations Population Division, issued in 2019, is that the world’s population will continue to grow for at least the rest of this century, reaching around 10.9 billion by 2100. A new forecast, planned for release later this year, will conclude much the same, chief UN demographer Patrick Gerland told me in December.
That’s bad news if you are among the doomsayers who see rising human numbers as the main driver of ever-increasing resource consumption, the stripping of natural ecosystems to provide land for agriculture, the flooding of the planet with toxic chemicals and plastics, and the further generation of climate-warming greenhouse gas emissions.
Against this backdrop, it might seem like declining populations would be a good thing, at least environmentally speaking.
Yet if demography does have something to say about destiny, too few people could soon be an even greater curse than too many. With fertility falling seriously below replacement level in many countries, demographers such as Wolfgang Lutz at the Wittgenstein Centre for Demography and Global Human Capital in Vienna have started warning of the danger of the world descending into a low-fertility trap, in which dramatic decreases in human numbers drive economic implosion, which results in insecurity that further discourages people from starting families.
In 2020, Stein Emil Vollset and colleagues at the Institute for Health Metrics and Evaluation at the University of Washington, for example, predicted that crashing fertility would see population numbers peaking in 2064, then falling sharply to just 8.8 billion by century’s end. “Continued global population growth through the century is no longer the most likely trajectory,” their study concluded.
Their projections are based in part on their models of underlying drivers of falling fertility, especially female education and the availability of contraception, which they say explains 80 percent of past fertility changes. The study calculated that if the UN Sustainable Development Goals for education, contraception, and gender equality were met in full, the world population by the end of the century could be as low as 6.3 billion, a fifth below today’s number.
Vollset and his colleagues warned that the results would be “extremely challenging,” as declining workforces cause nations’ economies to implode. That poses problems for addressing climate change. It is true that fewer people could mean less total consumption, reducing emissions. But it does not necessarily follow that such cuts would immediately solve the world’s environmental problems.
Scale is often necessary for the most efficient production of food and goods. It is also conducive to the innovation required to address the environmental challenges that are already baked into humanity’s future, regardless of who is born in the next decade, century, and beyond. Short of the kind of demographic apocalypse after which the future would no longer matter to humans, it is clear that only technological transformation can deliver the emissions cuts of 90 percent needed to halt climate change.
The Institute for Health Metrics and Evaluation and its director, Christopher Murray, are not without detractors. Both have attracted criticism for reaching headline-grabbing conclusions from debatable projections and assumptions. Jane O’Sullivan of the University of Queensland, for example, expects fertility declines in Africa to be much slower than the institute grants, for a number of reasons. Moreover, she points out, their projections do “a great disservice to women’s reproductive rights.” What happens, for example, if governments, worried about population declines, limit contraception and other reproductive choices?
But many others, including Monica Das Gupta, a sociologist at the Maryland Population Research Center, believe Murray and Vollset are onto something. “It is entirely possible that their estimates are better than the UN ones,” Das Gupta told me. And indeed, a less-controversial 2014 prediction by a leading research group headed by Lutz also found global population peaking around 2070, though with much less decline thereafter.
Where Babies Come From
So who is right—and why does it matter? Two big questions dominate this debate. One is how fast fertility will fall in countries where it is still high; the other is whether countries with already very low fertility rates will bounce back to levels nearer to what’s needed for a stable population.
The ever-diminishing band of high-fertility nations includes Asian and Middle Eastern countries such as Afghanistan, Pakistan, Iraq, and Yemen, which all have fertility rates above 3.5, and most of sub-Saharan Africa, which averages 4.7. The latter is almost twice the 2019 global average fertility rate of 2.4 according to the World Bank. Will these countries eventually follow the path of Europe and East Asia?
Several factors may explain why rates in sub-Saharan Africa remain higher than elsewhere. One factor is that child death rates remain higher in Africa than elsewhere. Taking sex ratios at birth, age at death, and age-specific fertility rates into account, one study estimated the real “replacement rate of fertility” (RRF) in the sub-Saharan Africa countries of Chad, Central African Republic, and Nigeria to be 2.7—higher than the global RRF of 2.1 but not as stark a contrast as for the fertility rate.
Greater educational opportunities for girls and women, development experts have long maintained, play a large role in fertility choices. In that regard, one important factor in the still-high fertility rate in much of Africa, Lutz and his colleagues suggest, was the austerity program imposed by the International Monetary Fund and others in the 1980s, which resulted in decreased spending on education. As an example, they point to Kenya. In the 1970s, it had the world’s highest fertility rate of 8.1 children per child-bearer. This figure declined dramatically to just below 5 in the late 1990s, but then stalled there for about a decade, before declining again soon after the government revived its investment in secondary schooling. Today, he told me, the fertility rate in Kenya stands at about 3.4 children. Their study concluded that, without the decade lost to austerity, fertility rates across sub-Saharan Africa may well be about 0.5 children lower.
UN projections, based on crude past fertility trends, assume that childbearing will continue to decline in many African countries, but only slowly—near the rates seen after the austerity programs. By the end of the century, the UN predicts that two-thirds of sub-Saharan Africa will still have fertility above 2.1, enough to push its population from the current 1.1 billion people to 3.8 billion by 2100.
But Lutz and Vollset see the Kenyan experience as key, expecting accelerated fertility declines on a par with other nations as the continent urbanizes, education improves, and contraception is more accessible.
If that happens, for many people, it will represent a good thing—for health, for economic prospects, for personal choice, and more. But inasmuch as stark populations declines could eventually lead to depopulated landscapes, a weaker workforce, slower economic growth and innovation, it may also represent a challenge. And it is worth keeping both possibilities in mind.
The demographic future of countries where fertility is already well below replacement levels is also a major issue—because it involves more people and because each of those people has a much bigger planetary footprint. In Europe, fertility rates in Greece, Italy, Portugal, and Spain are between 1.4 and 1.5. In Asia, rates in Taiwan, Japan, and Singapore have fallen well below 1.5, and recent data put South Korea at below 0.9, a world record. These countries are becoming societies in which schools are emptying, a large fraction of people—through choice or economic insecurity—never have children, each generation is smaller than the last, and the average age of the population is creeping up towards 50 years. In Japan, the number of children under 14 is projected to halve by 2050, and hundreds of schools, especially in rural areas, close each year.
Some of today’s ultra-low fertility levels could be misleading—a result of a generation delaying childbirth from their 20s into their 30s. The rate could bounce back as people expand their families later; since 2000, for example, Germany’s fertility rate has risen from 1.3 to 1.6. At the UN, Gerland believes such rebounds will happen more widely, and his modeling assumes that low-fertility countries will all gravitate towards 1.75 by century’s end. But others question the rationale. “I don’t see any empirical evidence to support it,” Das Gupta told me. Vollset concurs, pointing to Thailand, South Korea, Greece, and Canada, which, unlike Germany, have not shown any bounce-back.
Still, whether rates converge at 1.75 because of bounce-backs or hit 1.3, both figures are below replacement level. And that means populations will decline either way. It is just a matter of how soon—and how steeply. Vollset, for his part, sees Japan, China, Thailand, Italy, Ukraine, and Spain all halving their populations by 2100, with dozens more down by more than a quarter. Governments may be powerless to prevent this. Australia, Russia, Singapore, and other low-fertility countries have already offered cash “baby bonuses,” tax breaks, welfare payments, and mortgage subsidies to encourage couples to have more children. All have failed.
And in the last two years, the pandemic has compounded broader trends. From China to Spain, birth rates have largely fallen during the COVID-19 pandemic, in some places to record lows. Far from using lockdown to make babies, people have been avoiding incurring extra financial burdens. Whether this proves temporary or a new downward driver on long-term fertility remains to be seen.
For some, these fertility rate declines can only be good news for the climate. Others see a future where economic growth could be harder to come by, where workforces are replenished less each year, and where innovation sputters.
Demography Is Not Destiny
But how much do such predictions matter?
Demographers and policy makers often assign great economic, environmental, and geopolitical significance to long-term population trends. In the past, Ehrlich-style warnings of high fertility rates have triggered aggressive and sometimes coercive political programs to prevent childbirths. And these days, warnings of the damaging effect of low-fertility rates have already prompted pro-natalist policies ranging from the apparently benign, including cash bonuses and tax breaks for having more children, to the more sinister reduced investment in contraceptive services and even propaganda on the virtues of women who devote their lives to childbearing.
But is it really true that demography determines national destiny?
Even Ehrlich conceded that the impact of human activity on the planet came down not just to numbers. Rather, it arose from a combination of three factors: human population, consumption patterns, and the technology used to produce what we consume.
Many environmental indicators, such as tree cover, improve as population increases. With more people to work the land, agricultural techniques often become more efficient, meaning people can produce more food on less acreage. Indeed, global agricultural land use has likely already peaked, based on work by environmental scientist Jesse Ausubel and others. Meanwhile, the precise energy-generating technologies a society uses are a far more important factor in carbon-dioxide emissions than the size of the population.
The argument that demographic decline could carry profound dangers is based largely on fears about aging populations. Vollset and his colleagues’ scenario estimated that the average age of humans, currently 33 years, will reach 46 by 2100. More than a quarter of us will then be over 65, Vollset says. Japan is at that level already. Its demographers argue that the combination of more old people to support and an aging and less innovative workforce is creating demographic enfeeblement and economic stagnation.
Likewise, in abandoning their one-child policy, Chinese leaders spoke of the fear of their country “getting old before it gets rich.” Vollset’s framing of the issue is similar. He told me that as China’s demographic boom turns to bust, it will likely deliver an economic gut punch. China, he believes, will overtake the United States as the biggest economy in the 2030s, but will then fall behind again later in the century as its population declines.
Or maybe China’s future is different. Das Gupta calls this presumed link between workforce and GDP “a curiously old-fashioned idea” in an era when IT savvy is likely to matter more for prosperity than large cohorts of factory workers. And some crude predictions seem improbable. Most analysts expect Nigeria to more than triple its current population and become the second or third most populous nation by 2100. But that won’t turn it into an economic superpower on par with China, India, or the United States absent other changes.
And there, Lutz told me he identifies a “positive feedback loop between technological progress, human capital formation, fertility decline, and increasing survival” as underlying successful nations. In a joint paper last year, Marois, Gietel-Basten, and Lutz argued that China should do fine as it shrinks and ages, noting that “Human capital accumulation has been very strong—especially among younger cohorts.” China’s workforce may be smaller in number, but it will be well educated, able to power on with AI, robotics, and whatever other cutting-edge technologies are driving a smarter, less-polluting, and more-efficient world that can support the world’s population, whatever its size.
In other words, the interplay among human population, consumption patterns, and the technology we use to produce what we consume is too complex to say with certainly what a particular population size will mean for the planet.
So here is an optimistic narrative. The demographic doomsters on both sides are wrong. Whether they are the old kind of pessimists who saw disaster arising from a population “bomb” or the new kind who see a shrinking and aging population as driving nations to stagnation and decay, they do not have unique insights into national and human progress.
The future could be much more up for grabs. Investment in people—in education, health care, entrepreneurship, innovation, equality, and much else—will drive populations to greater well-being and prosperity. It could solve environmental problems too, eliminating or dramatically reducing climate change through new sources of energy; growing more food on dramatically less land; restoring nature to large areas of the planet; and maintaining the nitrogen, carbon, hydrological, and other planetary cycles essential to our sustainable occupation of the planet—whether those populations are growing or shrinking.
Demography is not destiny. Dynamic, innovative societies make their own futures. In healthy, well-educated, and egalitarian societies, we can stop worrying about fertility. People can have the children they want without pressure. Fertility can look after itself, and we can do the rest.