One in four people alive today already lives in a country whose population has already reached its peak and begun to decline, according to the United Nations World Population Prospects 2024 revision. Global population as a whole is still growing, and is projected to peak at roughly 10.3 billion people sometime in the mid-2080s before beginning a very gradual decline. But that global trajectory masks enormous divergence at the country level, where dozens of nations, overwhelmingly in East Asia and Europe, are already shrinking, some rapidly.
The word “collapse” gets used loosely in popular discussion of this topic, often applied to a single year of decline or a modest dip in the birth rate. This article defines it more precisely: sustained, multi year population decline driven by some combination of very low fertility, an aging population structure, deaths outnumbering births, and, in some cases, emigration exceeding immigration.
What Does Population Decline Actually Mean
Demographers distinguish between a temporary dip, often caused by a single economic shock or event, and structural decline, where the underlying age structure and fertility rate make continued population loss likely for decades regardless of short term policy interventions.
A country experiencing structural decline typically has a total fertility rate well below the replacement level of roughly 2.1 births per woman, combined with an aging population where deaths from an unusually large older cohort increasingly outnumber births from a much smaller younger cohort.
Which Countries Have Already Passed Their Population Peak
According to UN WPP 2024 analysis, one quarter of the global population, more than 2 billion people, already lives in a country where population has peaked and is now declining. This includes China, which the UN and most demographers agree peaked around 2021 to 2022 after decades of below replacement fertility following the one child policy era, as well as Japan, which peaked considerably earlier, around 2008 to 2010, and most countries across Central, Southern, and Eastern Europe.
Why Are Populations Shrinking
Very Low Fertility
Total fertility rates well below the 2.1 replacement threshold are the foundational driver in nearly every declining country. South Korea’s fertility rate has fallen to among the lowest ever recorded anywhere in the world, hovering in the range of 0.7 to 0.8 births per woman in recent years, meaning each generation is only about a third the size of the one before it if the rate persists.
Population Aging
Even after a fertility rate stabilizes or modestly recovers, population aging continues to work through the system for decades, a phenomenon demographers call population momentum operating in reverse. A country with a large elderly cohort and a small youth cohort will see deaths outnumber births for a sustained period even if fertility improves somewhat, simply because there are fewer women of childbearing age relative to the number of older people who will eventually die.
Deaths Exceeding Births
This is the proximate mechanical cause of decline in every case, sometimes called natural decrease. Japan, most of Eastern Europe, and increasingly China have all crossed this threshold, where the annual number of deaths now exceeds the annual number of births.
Emigration
In some countries, net emigration compounds natural decrease rather than causing decline on its own. Several Eastern European countries, including Bulgaria, Latvia, and Lithuania, have experienced both very low fertility and substantial emigration to wealthier EU countries since joining the European Union, producing some of the steepest percentage population declines recorded anywhere in the world in recent decades.
Population Decline Is Not the Same Everywhere
| Pattern | Example Countries | Primary Driver |
|---|---|---|
| Low fertility with net immigration offsetting decline | Germany, Italy (partial offset) | Fertility below replacement, immigration inflow |
| Low fertility with emigration compounding decline | Bulgaria, Latvia, Lithuania | Fertility below replacement plus outflow |
| Very low fertility, limited immigration | Japan, South Korea | Fertility below replacement, low immigration |
| Fertility collapse after one child policy era | China | Below replacement fertility, aging structure |
Germany and, to a lesser degree, Italy illustrate that immigration can meaningfully offset natural population decrease even where fertility remains well below replacement level, while Japan and South Korea illustrate the opposite pattern, where historically low immigration has left natural decrease largely unaddressed.
The Age Structure Problem
Population aging is, in a mechanical sense, locked in for decades once a country’s fertility rate falls and stays low for an extended period, because the smaller youth cohort born during the low fertility years eventually becomes the working age and childbearing age population, constraining both future births and future workforce size simultaneously. This is why demographers describe fertility recovery, even a fairly dramatic one, as taking twenty to thirty years to meaningfully shift a country’s overall age structure and growth trajectory.
Can Immigration Prevent Population Decline
For some countries, yes, at least partially and for a period of time. The UN’s WPP 2024 revision projects that immigration will become the main driver of population growth in 52 countries by 2054, a striking figure that reflects how many countries with fertility already below replacement level are expected to depend on immigration rather than natural increase to avoid outright decline.
However, immigration alone does not resolve the underlying age structure problem, since immigrants themselves eventually age, and sustained immigration at a high enough level to offset very low fertility indefinitely faces both political and practical limits in most countries.
What Population Decline Means for Economies and Communities
A shrinking working age population directly constrains labor supply and economic growth potential, all else being equal, while a growing elderly population increases demand on pension systems and healthcare simultaneously. Rural depopulation, school closures, and declining local tax bases are common secondary effects in regions experiencing the steepest population loss, a pattern already visible across large parts of rural Japan and Eastern Europe, where entire towns have seen population fall by a third or more over a generation.
Which Countries Could Lose the Most People by 2050
UN WPP 2024 projections indicate that China, Japan, and several Eastern European countries are likely to see some of the largest population declines in absolute and percentage terms respectively over the coming decades, though these figures should be understood as projections based on current fertility, mortality, and migration assumptions rather than certainties, since fertility rates in particular have historically proven difficult to forecast accurately over multi decade horizons.
Is Global Population Decline Coming
Not in the near term. Global population is still projected to grow from 8.2 billion in 2024 to a peak of roughly 10.3 billion in the mid-2080s, driven overwhelmingly by continued growth in Sub-Saharan Africa and, to a lesser degree, parts of South Asia. What is already true is that a quarter of humanity lives in a country where the national, rather than global, peak has already passed, illustrating how uneven the timing of demographic transition has become across different world regions.
Key Findings
- One quarter of the global population, more than 2 billion people, already lives in a country whose population has peaked and begun to decline.
- China’s population is generally understood by demographers to have peaked around 2021 to 2022; Japan’s peaked considerably earlier, around 2008 to 2010.
- South Korea’s fertility rate has fallen to roughly 0.7 to 0.8 births per woman in recent years, among the lowest ever recorded globally.
- Immigration is projected to become the main driver of population growth in 52 countries by 2054, according to UN WPP 2024.
- Global population is still projected to grow to a peak of roughly 10.3 billion in the mid-2080s, even as many individual countries are already shrinking.
Frequently Asked Questions
1. Which countries are losing population fastest?
Bulgaria, Latvia, and Lithuania rank among the countries with the steepest percentage population declines, driven by a combination of very low fertility and substantial emigration since joining the European Union, while China and Japan have the largest declines in absolute population terms.
2. What causes population collapse?
Very low fertility rates below the 2.1 replacement threshold, an aging population structure that causes deaths to outnumber births, and in some countries, emigration exceeding immigration, together drive sustained population decline.
3. Has China’s population actually peaked?
Most demographers, including the UN, place China’s population peak around 2021 to 2022, following decades of below replacement fertility that trace back to the one child policy era and its lasting effects on family size norms.
4. Can immigration stop population decline?
In some countries, yes, at least partially. Germany’s population has been meaningfully sustained by immigration despite fertility well below replacement level, though immigration alone does not fully resolve the underlying age structure challenges of a shrinking, aging population.
5. Is the world’s population shrinking?
No, not yet. Global population is projected to keep growing to a peak of roughly 10.3 billion around the mid-2080s, driven by continued growth in Sub-Saharan Africa, even though many individual countries are already in decline.
6. What is South Korea’s fertility rate?
South Korea’s total fertility rate has fallen to roughly 0.7 to 0.8 births per woman in recent years, among the lowest ever recorded for any country.
7. How many countries will rely on immigration for growth by 2054?
The UN’s 2024 population projections indicate that 52 countries will depend on immigration as their main source of population growth by 2054, reflecting how widespread below replacement fertility has become.
8. What happens to an economy when population declines?
Labor supply and economic growth potential generally face downward pressure, while pension and healthcare systems face increased demand from a growing share of elderly residents relative to working age taxpayers.
9. Can a country reverse population decline once it starts?
It is very difficult in the short term, since population aging effects persist for decades even after fertility improves, a lag demographers estimate at twenty to thirty years before a fertility recovery meaningfully shifts overall population trajectory.
10. Why do some declining countries lose population faster than others?
Countries combining very low fertility with substantial emigration, such as several Eastern European nations, tend to see faster percentage decline than countries with similarly low fertility but significant immigration inflows, such as Germany.
Sources
- United Nations, World Population Prospects 2024 revision
- United Nations Department of Economic and Social Affairs, Population Division
- National statistical agencies of China, Japan, South Korea, and EU member states
