The world's population is likely to peak much earlier and at a much lower level than experts have predicted. Rather than climbing until 2084 to 10.3bn people, as the United Nations foresees, it may stop growing in the 2050s and never exceed 9bn. If current trends continue for just ten more years before the UN's more optimistic assumptions kick in, the global population peaks at 9.6bn in 2065, then tumbles to 8.9bn by 2100. Even that may be too optimistic. The world's population soared from 1bn in 1800 to 8bn today; sub-replacement fertility implies it will shrink slowly at first and then dramatically, in a mirror image of that exponential growth. At that point, the world's population will start to shrink—something it has not done since the 14th century, when the Black Death wiped out perhaps a fifth of humanity.
Fertility rates have been dropping for centuries, mostly for benign reasons: social-security systems, lower childhood mortality, the liberation of women, and greater access to contraception. What is striking is that the decline is accelerating. The pace of global falls doubled between the 2000s and 2010s and has doubled again in the current decade, sinking on average by almost 2% a year.
Only about one-third of the world's people live in countries where fertility is high enough to keep the population growing, and even in those places rates are falling rapidly. Africa still produces many more babies than the global norm, but is no exception to the rule of faster-than-expected declines.
The replacement fertility rate—the level needed to keep a population stable in the long run—is about 2.1 children per woman.
The UN projects that all countries that have transitioned to low fertility will follow one of only two trajectories: stabilisation or an increase in baby-making. It expects no country's fertility rate to continue falling. The improbable implication is that low fertility is a self-correcting problem and that the correction will begin immediately in some of the worst-afflicted countries.
Anne Goujon of the IIASA, an institute in Austria that releases rival population projections, calls the expectation of a rebound in fertility "a bit of wishful thinking". The IIASA is preparing to include scenarios in which declining fertility persists.
John Wilmoth of the United Nations Population Division offers one rationale for the idea that fertility rates will rebound: "an expectation of continuing social progress towards gender equality and women's empowerment". But the record of women's empowerment thus far around the world is that it leads to lower fertility rates. Wilmoth concedes this is not "an air-tight case".
Lant Pritchett of the London School of Economics notes that "replacement fertility is a knife-edge. Over the very long run, humans shrink to zero or swell to huge numbers, depending on whether they stay below or above the replacement rate."
| Country | Total fertility rate | Notes |
|---|---|---|
| South Korea | 0.72 | Below one for seven years; population could halve in a single lifetime if sustained |
| Bogotá, Colombia | 0.91 | Lower than Tokyo |
| Colombia (national) | ~1.06–1.2 | Dropped to 1.2 in 2023; may have fallen as low as 1.06 in 2024 |
| Thailand | 1.0 | The UN had expected 1.2 in 2024 |
| Delhi, India | 1.2 | |
| Turkey | 1.48 | Well below replacement; the UN thought it would not fall so low until at least 2100 |
| Mexico | 1.6 | About the same as the United States |
| United States | 1.6 | Fallen almost continuously from 1.9 in 2010 |
| India (national) | 1.9 | Below replacement; bound to start shrinking around mid-century |
France recorded fewer births in 2024 than in 1806, when the population was less than half its current size. Italy registered its lowest birth count since unification in 1861. Fewer than 2m babies were born in Egypt in 2024, a threshold it was not expected to cross before 2100. Birth rates have fallen by a fifth in Nordic countries since 2010. China's population is already contracting.
A shrinking population will have profound consequences—turning expectations about housing, greenhouse-gas emissions, labour forces and consumer markets upside down—but need not be catastrophic. The insinuation that human societies cannot flourish without expanding rests on flimsy evidence.
Fewer people means less economic growth and potentially lower tax receipts, making government debt harder to sustain. But the IMF reckons ageing societies will save more for retirement, forcing down returns and interest rates, which would let governments service their debts more easily.
The critical economic factor is not the number of people but the number in work. Raising labour-force participation could compensate for a big contraction of the working-age population. In Britain, roughly 9m of 43m working-age adults were neither in work nor in full-time education in 2024; the Office for National Statistics reckons the working-age population will contract by just 7% from its peak by 2100. A Goldman Sachs study found that the typical worker in a rich country now toils four years longer than in 2000. The average 70-year-old in 2022 had the same cognitive abilities as a 53-year-old in 2000.
The British state spends more each year on the average person below 25, mostly on education and health care, than it does on health care and pensions for a typical old person.
Larger populations tend to generate more research and set up more businesses. The slowing growth of America's labour force accounts for around a third of the recent fall in the creation of new businesses. Yet the world seems far from exhausting its capacity for innovation. Israel employs a greater share of the workforce in research and development than any other country but still devotes only 1% of workers to it. In Pakistan fewer than one in 10,000 people works in technology or research.
Charles Jones and Nick Bloom, both economists at Stanford, documented how researchers were making fewer discoveries than in the past—the speed of innovation was slowing. Jones now thinks artificial intelligence could aid the search for frontier ideas.
Investment will be depressed in economies with shrinking populations, but such places benefit from "capital deepening" as the capital stock per person rises, pushing up productivity. David Weil, an economist at Brown University, modelled the wider economic effects of consistently low or high fertility rates and found that consumption per person differed little regardless of whether the population was growing or shrinking.
Noise proves nothing. Often a hen who has merely laid an egg cackles as if she laid an asteroid.