A child born this year will, by the time they reach late middle age, almost certainly live in a world where the human population is no longer growing. By the time that same child reaches retirement, the population will, on the available projections, have begun to shrink. This is not a fringe demographic claim. It is the central finding of the most recent set of population projections published by the United Nations Department of Economic and Social Affairs, released on World Population Day in July 2024. The report, drawing on data from 1,910 censuses across 237 countries and territories, projects that the global population will peak at approximately 10.3 billion people in the mid-2080s, plateau briefly, and then decline to approximately 10.2 billion by the year 2100. The peak is now expected slightly earlier and slightly lower than the 2022 projections suggested, primarily because fertility rates in several large countries — China most prominently — have fallen substantially faster than demographers had anticipated.
According to the UN’s official World Population Prospects 2024 Summary of Results, the probability that the global population will peak within the current century is now estimated at approximately 80 percent — up substantially from the roughly 30 percent the UN was estimating in 2013. The shift reflects a steady accumulation of evidence over the past decade that fertility rates worldwide are declining faster than mid-twentieth-century demographers had expected. The global fertility rate now sits at approximately 2.25 children per woman, just above the replacement level of 2.1 needed to maintain a stable population. The global rate is projected to cross below replacement in approximately 2036 — within the next decade — at which point the only thing keeping the human population growing will be the demographic momentum of large existing cohorts of young adults still in their reproductive years.
What the country-level data show
The aggregate global figures conceal an extraordinary divergence across countries. Per Population Connection’s analysis of the 2024 UN projections, the populations of 63 countries had already peaked before 2024 — including China, Germany, Japan, Italy, and South Korea — and are now in active decline. An additional 48 countries are projected to peak between 2025 and 2054, covering approximately a tenth of the current world population. Among the lowest fertility rates currently recorded are South Korea at approximately 0.7 children per woman, Hong Kong at 0.8, Taiwan at 0.9, Singapore at 1.0, and China at 1.0 — figures so far below replacement that, absent immigration, these populations will halve every 35 to 50 years on current trajectories. Japan, Italy, and Spain sit at approximately 1.2. Most of Eastern Europe, Northeast Asia, and Southern Europe is now well below 1.5.
At the other end of the distribution, the countries with the highest current fertility rates are concentrated in sub-Saharan Africa. Niger has the world’s highest rate at approximately 6.6 children per woman, followed by Somalia (~6.0), Chad (~5.9), Mali (~5.7), the Democratic Republic of Congo (~5.4), and Nigeria (~5.0). Sub-Saharan Africa as a whole is projected to add approximately 1 billion people by 2054 — accounting for essentially all of the remaining global population growth through the century. The combination of rapid decline in most of the world and continued growth in Africa means that the demographic composition of the species is shifting substantially. By 2100, more than 40 percent of children under five globally will be African, compared to approximately 25 percent today.
Why the trajectory is hard to reverse
The features of the demographic transition that make it particularly difficult to undo were laid out in detail by the UN demographers in their 2024 report. As reported by the French National Institute of Demographic Studies (INED) in its summary of the UN findings, for the 24 countries already at ultra-low fertility with peaked populations, the probability of fertility rates returning to 2.1 or higher within the next 30 years is approximately 0.1 percent — essentially zero. The reason is structural rather than cultural. By the late 2030s, half of the women in those countries will be too old to have children by natural means. Even if pro-natalist policies somehow succeeded in raising the per-woman fertility rate substantially, the absolute number of women in their childbearing years will have contracted so much that total births would continue to fall. The demographic momentum runs in both directions: just as a large cohort of young adults can sustain population growth even at sub-replacement fertility, a small cohort of young adults will produce population decline even if individual fertility rates rise.
The countries that have implemented serious pro-natalist policies — South Korea, Hungary, Singapore, China, Japan — have, to date, produced essentially no measurable effect on fertility rates. Cash payments, parental leave extensions, childcare subsidies, fertility treatment coverage, and direct propaganda campaigns have all been tried, and the rates have continued to fall. The reasons are debated. Most demographers attribute the decline to some combination of education and labour-market participation by women, the rising direct and opportunity costs of raising children in high-income economies, urbanization, housing costs, the prevalence of contraception, changing cultural expectations about parenthood, and the broader transition of children from economic assets to economic costs that has characterised industrialised societies since the mid-twentieth century.
What the end of growth means
As discussed in Population Matters’ overview of the 2024 UN projections, the implications for the structure of human societies are substantial and not yet well-absorbed by most economic and political institutions. By 2080, people aged 65 and older will outnumber children under 18 globally. By the mid-2030s, people aged 80 and over will already outnumber infants worldwide. The age structure of the species is inverting in real time, with consequences for labour markets, pension systems, healthcare infrastructure, military demographics, real estate markets, and essentially every institution that was designed for an expanding population. Immigration will become the primary driver of population growth in approximately 52 countries through 2054 — including the United States, Canada, Australia, and the United Kingdom — meaning the political contests around immigration will, for most of the rest of the 21st century, become inseparable from the demographic survival of the receiving societies.
The Black Death, in the 14th century, was a brief and catastrophic event that killed an estimated 30 to 60 percent of the European population within a few years. The current demographic shift is the opposite kind of phenomenon — slow, voluntary, distributed across decades, and the product of billions of individual decisions about when and whether to have children. The Black Death population decline lasted approximately 150 years before growth resumed. The current decline, on the available projections, has no clear end date in view. Some recent research — notably by the demographer Dean Spears at the University of Texas — argues that the UN projections themselves still overestimate future fertility, and that the global peak may come as early as 2061 at approximately 9.5 billion, rather than the 10.3 billion the UN models project. Whether the peak arrives in 2061 or 2084, the basic direction of the trajectory is no longer in serious dispute among demographers. The era of sustained human population growth — which produced essentially all of the institutional infrastructure of modern civilisation — is ending. The next several centuries will be the first sustained test of how human societies function when the species is contracting rather than expanding.
