The United Nations expects the global population to peak at around 10.3 billion people in the mid-2080s, then begin a slow decline, ending the century at roughly 10.2 billion, a level 700 million lower, 6 percent below, what the UN itself projected just a decade earlier. That downward revision alone tells you something important about the future of population forecasting: fertility is falling faster than expected in some of the world’s largest countries, and the world’s demographic future is being rewritten in real time even as it unfolds. Four structural forces, population size, aging, migration, and urbanization, will determine what that future actually looks like on the ground.
The Global Population Outlook
The world’s population stood at approximately 8.2 billion in 2024 and is projected to keep growing for another 50 to 60 years, reaching a peak of around 10.3 billion in the mid-2080s before beginning a gradual decline toward approximately 10.2 billion by 2100.
This later peak and subsequent decline mark a meaningful departure from the previous generation of UN projections, which anticipated continued growth through 2100 without a peak in sight; the 2024 revision’s lower trajectory stems mainly from fertility levels falling faster than previously modeled in several of the world’s most populous countries, especially China.
Global Population Trajectory, Estimated and Projected
| Year | Global Population | Status |
|---|---|---|
| 1950 | 2.5 billion | Historical |
| 2024 | 8.2 billion | Current estimate |
| Mid-2080s | approximately 10.3 billion | Projected peak (medium variant) |
| 2100 | approximately 10.2 billion | Projected (medium variant), following decline from peak |
Source: United Nations World Population Prospects 2024: Summary of Results. Figures beyond 2024 are medium-variant projections, not certainties, and should be read as the UN’s current best scenario rather than a fixed outcome.
Where Population Will Grow
Future population growth will be extraordinarily concentrated. Nine countries, India, Nigeria, Pakistan, the Democratic Republic of Congo, Ethiopia, Tanzania, the United States, Indonesia, and Uganda, are expected to account for more than half of all global population growth over coming decades, with sub-Saharan Africa contributing the largest regional share by far.
Within that region, several countries, including Angola, the Central African Republic, the Democratic Republic of Congo, Niger, and Somalia, are projected to double their populations between 2024 and 2054 alone, a pace of sustained national growth with few historical precedents.
Where Population Will Shrink
At the opposite end of the spectrum, 63 countries and areas, home to 28 percent of the world’s population in 2024, have already passed peak population size, including China, Germany, Japan, Italy, and Russia. Their combined population is projected to decline by 14 percent over the next 30 years.
China’s case is the most consequential given its size: it is projected to lose 204 million people between 2024 and 2054, and by 2100 its population is expected to fall to just 633 million, a level last seen in the late 1950s and representing a loss of more than half its current population.
A further 48 countries, including Brazil, Iran, Turkey, and Vietnam, are projected to peak between 2025 and 2054, meaning the group of shrinking countries will continue to grow throughout this century even as the global total keeps rising for several more decades.
The Aging of Humanity
Population aging is arguably the most consequential and least reversible of the four structural forces covered here, because unlike population size, which responds relatively quickly to changes in fertility, age structure changes are locked in decades in advance by cohorts already alive today. Global life expectancy at birth reached 73.3 years in 2024, up 8.4 years since 1995, and is projected to climb to approximately 77.4 years by 2054.
The consequences for age structure are dramatic and specifically dated by UN researchers: by 2080, the number of people aged 65 and older is expected to surpass the number of children under 18 globally for the first time, and by the mid-2030s, the number of people aged 80 and older is expected to outnumber the number of infants worldwide.
Within the group of 63 countries that have already peaked in population, this milestone arrives much sooner: the number of people aged 65 and older in that group is projected to reach 409 million by 2027, already surpassing the number of children under 18 there.
Migration as a Demographic Force
Migration is the one component of population change that policy can influence relatively directly and quickly, compared to the multi-decade lags inherent in fertility and mortality shifts, and the UN’s own analysis identifies it as a major factor already reshaping the trajectory of several low-fertility countries.
Net immigration has specifically delayed peak population timing in Italy, Germany, and Russia, countries that would otherwise have seen their populations peak and begin declining earlier than they actually have, purely on the strength of their underlying fertility and mortality trends.
Whether immigration can do more than delay decline, actually reversing it on a sustained basis, remains an open and actively debated question, since the scale of migration required to fully offset a large fertility deficit is substantial, and migrants’ own fertility behavior tends to converge toward destination-country norms within a generation or two, limiting how permanently immigration alone can reshape a country’s demographic trajectory.
The Future of Cities
Urbanization is reshaping where the world’s population physically lives at a pace that rivals any other demographic shift covered here. Cities were already home to 45 percent of the world’s 8.2 billion people as of the UN’s World Urbanization Prospects 2025, more than double the 20 percent share recorded in 1950, and two-thirds of all global population growth between now and 2050 is projected to occur within cities, with most of the remaining growth occurring in towns rather than rural areas, which are expected to peak in population in the 2040s before beginning to decline in absolute terms.
Global Megacity Growth, 1975 to 2050
| Year | Number of Megacities (10 million or more inhabitants) | Notable Detail |
|---|---|---|
| 1975 | 8 | Starting baseline |
| 2025 | 33 | 19 located in Asia; Jakarta, Dhaka, and Tokyo are the three largest |
| 2050 (projected) | 37 | Addis Ababa, Dar es Salaam, Hajipur, and Kuala Lumpur projected to newly cross the 10 million threshold |
Source: United Nations World Urbanization Prospects 2025: Summary of Results, released November 18, 2025.
Jakarta has overtaken the megacity rankings to become the world’s most populous city, with nearly 42 million residents, ahead of Dhaka at roughly 37 to 40 million and Tokyo at approximately 33 million; Dhaka, still growing rapidly, is projected to become the world’s single largest city by mid-century, while Tokyo’s population is projected to shrink enough that it falls to seventh rank by 2050, a striking illustration of how population decline and urban growth can operate on entirely different trajectories even within the same country.
Despite the prominence of megacities in public discussion, the UN’s data shows that most of the world’s urban population actually lives in small and medium-sized cities rather than megacities: of roughly 12,000 cities analyzed worldwide, 96 percent have fewer than 1 million inhabitants, and these smaller cities are, in many cases, growing faster than the megacities that receive most media attention, particularly across Africa and Asia.
Seven countries, India, Nigeria, Pakistan, the Democratic Republic of Congo, Egypt, Bangladesh, and Ethiopia, are projected to account for more than half of all urban population growth between 2025 and 2050, together adding more than 500 million new city residents.
The Future Workforce
Population age structure translates directly into future labor supply, and the divergent trajectories of growing and shrinking countries point toward sharply different workforce futures. Countries with young, still-growing populations, concentrated in sub-Saharan Africa and South Asia, face the challenge of generating enough jobs to absorb historically large cohorts of young workers entering the labor market simultaneously, a test of whether rapid population growth becomes an economic asset or a source of youth unemployment.
Countries with aging, shrinking populations face the opposite structural problem: a contracting working-age base that must support a rapidly growing population of retirees, a dynamic already straining pension and healthcare financing in Japan, much of Europe, and increasingly China, and one that has prompted growing policy interest in longer working lives, automation, and productivity gains as partial offsets to a shrinking labor supply.
What Could Change the Forecast?
The UN’s own projection history is itself the clearest evidence that these forecasts carry genuine uncertainty rather than false precision. The 2024 revision lowered the projected 2100 global population by roughly 700 million people, or 6 percent, compared to the UN’s 2013-era projections, driven primarily by fertility falling faster than modeled in several major countries, especially China.
Fertility remains the single largest source of uncertainty in any long-run population projection, since it depends on social, economic, and policy factors that are inherently difficult to forecast decades in advance, far more so than mortality, which tends to change more gradually and predictably, or migration, which, while volatile year to year, has a smaller cumulative effect on total population size than sustained shifts in fertility.
What the Future Population Could Mean for Resources and Society
The four forces described here interact to create very different practical pressures depending on where in the world one looks. In fast-growing, young countries, the priority pressures concern building enough schools, generating enough jobs, and expanding infrastructure and food systems fast enough to keep pace with rapidly growing populations, challenges the UN has repeatedly flagged as being especially acute because they are concentrated in some of the world’s lower-income countries.
In aging, shrinking countries, the priority pressures shift toward healthcare capacity for a growing elderly population, pension system sustainability under a narrowing worker-to-retiree ratio, and, in the most rapidly urbanizing and depopulating regions simultaneously, managing the uneven decline of some cities and rural areas alongside continued growth in others.
Neither set of pressures admits a simple, universal policy answer, and the UN’s own framing consistently emphasizes that demographic trends create both risks and opportunities depending on how effectively individual countries plan and invest in response to them.
Conclusion
The four forces shaping humanity’s demographic future, population size, aging, migration, and urbanization, are not moving in the same direction or at the same pace everywhere, and that divergence is itself the central story.
The world’s population will keep growing for another 50 to 60 years even as 63 countries have already begun shrinking; humanity is aging so fast that people over 80 will outnumber infants globally within roughly a decade, even as some of the fastest population growth in modern history continues in parts of sub-Saharan Africa; and cities are absorbing nearly all future population growth even as some of today’s largest cities, Tokyo chief among them, are projected to shrink.
The UN’s own willingness to revise its century-end projection downward by 700 million people in a single decade is perhaps the most important takeaway of all: this future is not fixed, and the actual path fertility takes in the coming years will do more to determine it than any other single variable.
Frequently Asked Questions
1. What will the world population be in 2050?
The UN’s medium-variant projection has global population continuing to rise through 2050, on its way toward a peak of approximately 10.3 billion in the mid-2080s, though the exact 2050 figure depends on which UN revision is consulted, since projections are periodically updated as new fertility and mortality data become available.
2. What will the world population be in 2100?
The UN’s 2024 revision projects a global population of approximately 10.2 billion in 2100, following a peak of around 10.3 billion in the mid-2080s and a subsequent slow decline, a figure roughly 700 million lower than the UN’s own decade-earlier projection for the same year.
3. Where will population grow the most in the future?
Sub-Saharan Africa will drive the largest share of future population growth, with nine countries overall, including India, Nigeria, Pakistan, and several other sub-Saharan African nations, expected to account for more than half of all global population growth in coming decades.
4. How will aging change the world population?
The number of people aged 65 and older is projected to surpass the number of children under 18 globally by 2080, and the number of people aged 80 and older is projected to outnumber infants worldwide by the mid-2030s, marking a fundamental structural shift in humanity’s age composition.
5. Will migration reverse population decline in low-fertility countries?
Migration has already delayed peak population timing in countries like Italy, Germany, and Russia, but it has not been shown to fully reverse fertility-driven decline on a sustained basis, both due to the scale of migration required and because migrants’ fertility tends to converge toward destination-country norms over time.
6. How many megacities will there be by 2050?
The UN projects the number of megacities, cities with 10 million or more inhabitants, will rise from 33 in 2025 to 37 by 2050, with Addis Ababa, Dar es Salaam, Hajipur, and Kuala Lumpur expected to newly cross the 10-million threshold.
7. Which city will be the world’s largest by 2050?
Dhaka, Bangladesh, currently the world’s second-largest city, is projected to become the world’s largest city by mid-century, overtaking Jakarta, while Tokyo, the current third-largest city, is projected to fall to seventh place as its population shrinks.
8. Is most of the world’s urban population living in megacities?
No. Despite their prominence in public discussion, most of the world’s urban residents live in small and medium-sized cities: of roughly 12,000 cities analyzed globally, 96 percent have fewer than 1 million inhabitants.
9. Why did the UN lower its population projections in 2024?
The UN’s 2024 revision projected a 2100 global population roughly 700 million lower, 6 percent below, its previous decade-old estimate, mainly because fertility rates fell faster than previously modeled in several major countries, particularly China.
10. What happens to the workforce as population ages?
Aging, shrinking countries face a contracting working-age population relative to a growing retiree population, straining pension and healthcare systems, while young, growing countries face the opposite challenge of generating enough jobs for historically large cohorts of new workers entering the labor market.
Sources
- United Nations Department of Economic and Social Affairs, World Population Prospects 2024: Summary of Results, July 11, 2024
- United Nations Department of Economic and Social Affairs, World Urbanization Prospects 2025: Summary of Results, November 18, 2025
- United Nations DESA, “Ten Key Messages,” World Urbanization Prospects 2025
- United Nations DESA Policy Brief No. 167, Leveraging Population Trends for a More Sustainable and Inclusive Future
- United Nations, “Our Growing Population,” global-issues population overview
