Our incredible shrinking planet

A person on an electric wheelchair at a park in Beijing, China on July 14, 2024. (Photo by Na Bian/Bloomberg via Getty Images)

If the 20th century was an era obsessed with the fear of a global population explosion – a time when governments, experts, and journalists fretted that population growth powered by high birth rates would soon outstrip the planet’s finite resources – the 21st century promises to be the opposite, a time when fears focus on the world’s population growing older and smaller.  

As experts begin studying the coming implosion, the tendency thus far has been to emphasize the negative. We read about falling government tax revenues, less productivity and innovation, strained finances, depopulated militaries, and small families struggling to care for more numerous and longer-living older relatives. But that is only one part of the possible future. As we start preparing for the coming changes – and prepare we must – some humility is in order, for two reasons. First, many of the demographic prognoses that dominated headlines in the last century proved wrong. And second, if there is one constant running through all of history, it is that humans are remarkably ingenious and adaptable. There are thus good reasons to believe that we will avoid disaster this time too – that a shrinking world may prove just as manageable as a growing one did. 

Older and fewer

Low birth rates are the sole reason we are heading toward global depopulation. Humanity’s life expectancy at birth has never been higher; in 2023, according to the U.N. Population Division (UNPD), the average lifespan worldwide was 73 years. 

The UNPD also estimates that more than 70% of humanity now lives in countries with below-replacement fertility rates – that is, childbearing patterns insufficient to assure long-term population stability in the absence of compensatory migration. On every continent but Africa, fertility levels have fallen below the replacement level, generally benchmarked at 2.1 births per woman during her lifetime. And birth rates are continuing to decline almost everywhere. 

The UNPD anticipates that the global population will peak in the year 2084 – at least, that is its current “medium variant” projection. Under this scenario, close to 40% of the people currently alive – a little over 3 billion people – will live to see that momentous demographic turning point. By the UNPD’s “low variant” projection, on the other hand, human numbers will top out in the year 2053 – roughly a generation from now. If that version of the future comes to pass, more than 6 billion people alive today, or almost three-quarters of our current population, will still be around when the planet begins its depopulation. 

But the world’s population could start shrinking even sooner than that. Childbearing rates are currently plunging to levels that demographers would not have deemed possible just a few years ago. In the Indian city of Kolkata, for example, the fertility rate has reportedly fallen to one birth per woman – less than half the replacement rate. Bogota, Colombia, is now down to 0.9 births per woman. Last year, South Korea hit a fertility rate of just 0.72 births per woman – barely a third of the level necessary to maintain its population. We don’t know how far such extremely low birth rates will spread, or how low fertility can go. But since recent developments have already taken us into a demographic reality almost no one would have imagined even a decade ago, it would seem incautious to assert that no further surprises lie ahead. 

Prolonged sub-replacement fertility levels have inescapable demographic consequences. The obvious effect is the shrinking of the younger cohorts – and, eventually, the shrinking of the total population. Less intuitively apparent but no less predictable is the pronounced aging of the population. Surprising as it may sound, low fertility – not greater longevity – is the most powerful force turning societies gray. Given the tremendous declines in fertility that have already been witnessed around the world over the past generation – a decline of nearly 60% since the 1960s – the aging of the world’s population is now essentially  unavoidable.  

For much of the world, this future looms immediately ahead, not over the horizon. For example, if South America follows its current trajectory, half of its population will be over age 42 by the year 2050. By that year, half of East Asia will be over 52. Contemporary demographers define an “aged society” as one where 14% of the population is 65 or older. Using that benchmark, if the UNPD’s medium projections prove correct, the world as a whole will qualify as aged in 2050, since 16% of the global population will be 65 or older. And that year, many countries will be at double the threshold for an aged society. Senior citizens will exceed 25% of the populations of Italy and Spain and account for nearly 31% of China’s population. In Japan and South Korea, the figure will be close to 40%. And that’s if there are no more unanticipated dips in fertility trends. 

Nursing care support robot during a demonstration in Nagoya, Achi Prefecture, Japan on February 23, 2015. (Photo by Kyodo News via Getty Images)

Can humanity cope?

These trends will present humanity with new and unfamiliar problems. As we contemplate them, only one thing is certain, but it’s a point worth stressing: We are a uniquely adaptable animal. Much of the inevitable angst about the prospect of an aging and shrinking human population is consequently unwarranted.  

Half a century ago, when I first started studying population and development, fear of a population explosion was pervasive in popular and intellectual circles – recall the runaway bestsellers The Limits of Growth and The Population Bomb. Other alarmist treatises in the genre included Famine 1975!, a book that took as its premise the certainty that the overpopulated “Third World” would run out of food and debated which poor countries the United States should allow to starve first. As that disquisition suggests, population alarmism led to some very ugly talk, some of it little more than thinly disguised eugenics. (Occasionally the eugenics went undisguised.) Uncritical Malthusian-tinged pessimism reached the most respectable academic and scientific circles during those years, as Rapid Population Growth, a 1971 study by the National Academy of Sciences, demonstrates. The scare even led to some truly tragic government strategies: Think of China’s monstrous one-child policy.  

So what happened? The world’s population has doubled – and then some – over the past 50 years. Despite this unprecedented surge in human numbers, we have nevertheless managed to cheat Malthus spectacularly, generating the greatest worldwide surge of economic development yet recorded in human history.  

Even though population growth took place mainly in developing regions, according to World Bank researchers, the fraction of humanity living in extreme poverty has plunged,  from roughly 50% in 1970 to about 8% on the eve of the COVID-19 pandemic. And despite ever-increasing demand for food, the long-term trend for cereals has been falling real prices for over a century. In a direct economic sense, lower real food prices mean that food is actually less scarce today than when the world population was much smaller. 

Thanks to human ingenuity and adaptation, we have not only accommodated a vastly larger planetary population since the 1960s but dramatically improved the material conditions of life for these growing human numbers. Demographic doomsayers from the heyday of the “population explosion” managed to get more or less all of this almost entirely wrong. 

We should keep this history in mind today as we consider the emerging anxiety about aging and depopulation. And we should remember how susceptible the academy and policymakers are to intellectual fads and groupthink. We will need clearer thinking – less fearful and doctrinaire – if we are to successfully confront the challenges posed by our collective future. 

A better tomorrow

Of course, it’s easy enough to see why people worry about the demographic realities that lie ahead. Social change always brings uncertainty, and uncertainty is scary. But there are reasons to be cautiously optimistic about the outlook for our world. 

The first is that global depopulation and aging will be occurring in the context of an ongoing revolution in human potential. Part of this revolution is occurring in the realm of health. Since 1900, global life expectancy at birth has risen from around 30 to well over 70. And this trend in longevity could continue. As far as we can tell, maximum life expectancies have been heading straight up for three successive centuries, and there are good reasons to believe we have not yet reached the limits of human longevity. 

We are also experiencing an extraordinary explosion in education. All around the world, the educational attainment of national populations is rising steadily. In 1950, according to calculations from the Wittgenstein Centre for Demography and Human Capital, almost half the world’s adults had never been to school; by 2020, that share had fallen to one in eight. That same year, about a sixth of the world’s adults had at least some higher education – roughly 10 times the share in 1950. By 2050, according to the Wittgenstein Centre, a quarter of the world’s adults will have at least some higher education, and if the study’s most optimistic prediction comes true, the proportion could approach 40%.  

Although the quality of schooling varies dramatically within and between countries, and quantifying the economic value of the ongoing knowledge explosion is not always straightforward, it is nevertheless clear that the market value of applied knowledge continues to increase. As the inventory of practical knowledge accumulates, the horizon of human capabilities extends correspondingly. The revolution in human potential is the underlying explanation for the leap in global income and wealth over the past two centuries. Since the start of the 20th century, global per capita output has soared; the Maddison Project estimates that it was more than seven times higher in 2022 than it was in 1900. Meanwhile, a team at Credit Suisse (now UBS) calculates that per capita personal wealth for the world as a whole has been rising exponentially for at least the past several decades. 

A student cleans their classroom at Sakiyama elementary school in Tamba, Hyogo Prefecture, Japan on March 15, 2024. (Photo by Buddhika Weerasinghe/Bloomberg via Getty Images)

To be clear: This updraft of human flourishing has not included every single country every single year of the past century. Much of sub-Saharan Africa saw health progress derailed for years by the HIV/AIDS plague. Russia, for its part, has somehow managed to achieve a “high schooling/low human capital” environment over the past generation or so, paradoxically juxtaposing first world levels of educational attainment with third world – or even fourth world – health patterns. (For example, as I have shown elsewhere, on the eve of the COVID-19 pandemic, adult survival chances were distinctly poorer in Russia than in Bangladesh, a nation the U.N. designates as one of the world’s least developed countries – even though Russian adults are estimated to have on average more mean years of schooling than counterparts in Austria and Spain.) These are genuine exceptions. But they are just that – exceptions. The general rule is steady and progressive improvement in human health, wealth, capabilities, and practical knowledge. 

The tremendous power of the ongoing revolution in human potential ought to make for cautious optimism that prosperity and living standards can be not only maintained but even progressively increased in a shrinking and aging world. Of course, doing so will require adaptations – to policies, social arrangements, and individual lifestyles. But most of these should not be unthinkable for the world’s most adaptable animal. Unlock the value of health, especially for older people. Live longer, work longer. Completely recast the government Ponzi scheme known as “pay-as-you-go social benefits.” And so on. If these challenges look daunting, it is only because we are thinking small. And thinking small is not how that most adaptable animal came to flourish. 

Family matters

If this all sounds too Pollyannaish, we should remember that at least two big problems loom on the horizon. 

The smaller one involves dementia or senescence. For some reason, two generations of life-science breakthroughs have done very little to improve treatment or offer cures for Alzheimer’s disease and other age-related neurological disorders. Despite the revolution in human health, the risk of dementia still increases exponentially with age, and with the 80-and-older population poised to grow at breathtaking speed around the world over the coming generation, the burden this imposes will have real and increasing costs – human, social, and economic. 

The larger issue is the implosion of the family. If we were all potentially productive robots spat out of a factory, with an expiration date of, say, 85 years after we were switched on, the trends described above would make for a happy ending. But we are not robots – we are social animals who begin and often end our lives as dependents. As the Creator noticed of Adam, we need to be around other animals of our kind. But global aging and population decline are mainly driven by a withering away of the family – the basic unit of human life up to this point.  

As an arithmetic matter, the graying of societies is driven much more by smaller families than longer lives. But longer lives do mean that middle-aged and even elderly children will increasingly be responsible for the care of their ancient parents. 

Consider the outlook for China, as mapped out in demographic simulations by my colleague Ashton Verdery of Penn State University and myself. In 2000, only a 10th or so of Chinese 60-somethings had any living parents; three-quarters of married 60-something couples had no parents or in-laws to look after. But by 2050, according to our simulations, it is likely that almost half of China’s 60-somethings will have one or more living parent – and that 70% of Chinese couples in their 60s will have at least one living parent or in-law, and that many will have two or more.  

And those prospective elders are the (relatively) lucky ones – at least they have descendants. With the rise in voluntary childlessness around the world, growing numbers of elders will have no relatives to count on, or at least no close ones. In Japan, for example, demographers reported in 2009 that according to trajectories at the time, almost 40% of the women born there in 1990 would never have biological children, and slightly more than half of them would finish their lives without biological grandchildren. More recent revisions to such projections suggest that those numbers might turn out to be even higher today, with a 2023 report suggesting that up to 42% of Japanese women born in 2005 could end up with no biological children. 

With childlessness now rising throughout East Asia, the rest of the region is also on track to follow Japan toward a family-poor future. East Asia already has the world’s lowest fertility level, so it should be no surprise that the implosion of the family will reverberate there first. But we can expect similar revolutions to eventually hit almost every other region on the planet. 

Will the most adaptable of animals be able to devise a hack to allow them to survive and thrive in a future without families as we have known them? That remains to be seen – and the fate of humanity may turn on the answer to that question. 

This essay draws on a 2023 presentation to a conference sponsored by the BCG Henderson Institute.