Nine countries are on track to account for more than half of all global population growth between now and mid-century, and none of them is the country most people would guess. The United Nations’ population projections have consistently named the same core group over successive revisions: India, Nigeria, Pakistan, the Democratic Republic of Congo, Ethiopia, Tanzania, the United States, Indonesia, and Uganda. Seven of those nine are in Africa or South Asia, and several are projected to see their populations double within a single generation, a pace of growth found almost nowhere else on Earth today.
Where Is Population Growing Fastest?
Two distinct questions get conflated whenever people ask “where is population growing fastest,” and separating them is essential for reading any ranking correctly.
The first question asks about percentage growth rate, how fast a population is expanding relative to its own current size, a measure on which small countries with high fertility can post extreme figures even while adding relatively few people in absolute terms.
The second question asks about absolute growth, how many additional people a country adds each year, a measure on which large countries with even moderate growth rates can dwarf the contribution of much faster-growing small nations.
The Countries Adding the Most People
By absolute contribution to future global population growth, the UN Population Division has repeatedly identified the same group of nine countries across its recent revisions: India, Nigeria, Pakistan, the Democratic Republic of Congo, Ethiopia, Tanzania, the United States, Indonesia, and Uganda, ranked by their expected contribution to total growth.
India’s population overtook China’s around 2023 to 2024 to become the world’s largest, and its continued growth, alongside Nigeria’s rapid expansion, anchors much of this list. Nigeria stands out in particular: currently the world’s seventh-largest country, it has the fastest-growing population among the ten most populous countries worldwide, and UN projections have consistently shown it on track to overtake the United States and become the world’s third most populous country by roughly mid-century.
Countries Projected to Drive Half of Global Population Growth Through Mid-Century
| Rank (by contribution to growth) | Country | Region | Notable Trajectory |
|---|---|---|---|
| 1 | India | South Asia | World’s most populous country as of the mid-2020s |
| 2 | Nigeria | Sub-Saharan Africa | Projected to overtake the US as third most populous by mid-century |
| 3 | Pakistan | South Asia | Sustained high fertility combined with large existing population base |
| 4 | Democratic Republic of Congo | Sub-Saharan Africa | Among countries projected to grow at least fivefold by 2100 |
| 5 | Ethiopia | Sub-Saharan Africa | Rapid growth combined with a still-young age structure |
| 6 | Tanzania | Sub-Saharan Africa | Projected to double between 2022 and 2050 |
| 7 | United States | Northern America | Growth driven mainly by immigration rather than fertility |
| 8 | Indonesia | Southeast Asia | Large population base with moderate but sustained growth |
| 9 | Uganda | Sub-Saharan Africa | One of the youngest population structures globally |
Source: United Nations Department of Economic and Social Affairs, Population Division, World Population Prospects, multiple recent revisions.
The Fastest Growing Regions
Sub-Saharan Africa is, by a wide margin, the region driving the largest share of future global population growth, and the UN’s own reporting has been explicit about the scale involved: populations across parts of sub-Saharan Africa are projected to double between 2022 and 2050 in many countries, and the UN’s 2024 revision identifies nine countries, including Angola, the Central African Republic, the Democratic Republic of Congo, Niger, and Somalia, where population is projected to double between 2024 and 2054 alone.
Looking further out to 2100, the UN has projected that ten African countries, Angola, Burundi, Democratic Republic of Congo, Malawi, Mali, Niger, Somalia, Uganda, Tanzania, and Zambia, will have increased their populations by at least a factor of five relative to earlier baselines.
Why Some Populations Are Growing So Quickly
Rapid population growth in these countries is not the product of any single factor but the interaction of three demographic conditions occurring simultaneously.
High fertility remains the primary driver: while the global fertility rate has fallen to approximately 2.25 births per woman, fertility across much of sub-Saharan Africa remains substantially higher, with UN data historically placing regional averages well above four births per woman in the most recent measured periods, more than double the replacement threshold of 2.1.
Falling mortality, especially declining child mortality, means that a larger share of each large birth cohort now survives into adulthood and its own reproductive years than in previous generations, amplifying the effect of continued high fertility on total population growth.
A young age structure compounds both of these factors: countries with a very high share of their population already under 25 have an inherently larger base of future parents already alive today, which sustains high absolute birth numbers even if fertility per woman begins to decline.
The Role of Young Populations
Population momentum, the tendency for growth to continue for one or more generations after fertility begins falling, is especially powerful in the world’s youngest countries, because such a large share of their population has not yet entered, or has only recently entered, its reproductive years.
A country where 45 or 50 percent of the population is under 15 has an enormous future cohort of potential parents already born, meaning that total births can remain high, or even continue rising, for decades even as the average number of children per woman gradually declines. This mechanism explains why demographers expect sub-Saharan Africa’s population growth to continue well past mid-century even as fertility rates there follow the global pattern of decline, just from a much higher starting point and on a longer timeline than has been observed in Asia or Latin America.
Population Growth Hotspots Through 2054
Under the UN’s medium-variant projection, 126 countries and areas, including India, Indonesia, Nigeria, Pakistan, and the United States, are expected to continue growing through at least 2054.
Within that larger group, nine countries stand out for exceptionally rapid growth: Angola, the Central African Republic, the Democratic Republic of Congo, Niger, and Somalia are among those specifically identified as being on track to double their populations between 2024 and 2054, a 30-year doubling that would represent one of the fastest sustained rates of national population growth recorded in modern demographic history.
What Rapid Population Growth Means
Fast population growth creates concrete, immediate pressure on the systems that serve each new, unusually large cohort as it moves through childhood and into the labor market. Education systems in rapidly growing countries face continuous pressure to build new classrooms and train new teachers simply to keep pace with each larger incoming cohort of school-age children, a challenge distinct from and additional to any effort to improve educational quality.
Employment systems face an even larger structural test roughly 15 to 20 years after each large birth cohort, when that cohort reaches working age simultaneously and must be absorbed into the labor market, a challenge UN officials have repeatedly flagged as one of the most significant development tests facing rapidly growing, high-fertility countries, particularly across sub-Saharan Africa.
Infrastructure, housing, healthcare capacity, and food systems all face similar compounding pressure, and UN officials have noted that population growth concentrated in some of the world’s poorest countries poses a particular challenge to global poverty reduction and sustainable development efforts precisely because it is occurring where resources to absorb it are often most constrained.
Growth Rate Versus Growth in Numbers
A concrete illustration clarifies why these two measures diverge so sharply. A country with 2 million people growing at 4 percent annually adds about 80,000 people in a year, a very high percentage rate on a small absolute base. A country with 200 million people growing at just 1.5 percent annually adds roughly 3 million people in that same year, a much larger absolute contribution to global population despite a substantially lower percentage rate.
This is precisely why Nigeria, India, and Pakistan dominate any list of countries driving absolute global population growth despite having growth rates well below the very highest percentage rates found in some smaller, faster-growing nations: their enormous existing population base means even a moderate percentage growth rate translates into millions of additional people each year.
Conclusion
The countries driving the next several decades of global population growth are not a random or shifting list; the same nine nations, India, Nigeria, Pakistan, the Democratic Republic of Congo, Ethiopia, Tanzania, the United States, Indonesia, and Uganda, have appeared consistently across successive UN population revisions as the group expected to account for more than half of humanity’s future growth.
What has changed across those revisions is the pace: several sub-Saharan African countries are now projected to double their populations within just 30 years, between 2024 and 2054, a rate of sustained national growth with few historical parallels.
The gap between percentage growth rate and absolute population added remains the single most important distinction for interpreting any of this data correctly, since it explains why a country like Nigeria, not the fastest percentage grower in the world, nonetheless sits near the top of every list of countries shaping the future size of humanity.
Frequently Asked Questions
1. Which countries have the fastest growing populations?
By contribution to absolute global population growth, the UN has consistently identified India, Nigeria, Pakistan, the Democratic Republic of Congo, Ethiopia, Tanzania, the United States, Indonesia, and Uganda as the nine countries expected to account for more than half of world population growth in coming decades.
2. Which countries are adding the most people?
India and Nigeria lead in absolute terms, with Nigeria in particular projected to overtake the United States to become the world’s third most populous country by around mid-century due to its exceptionally rapid growth among the world’s ten largest countries.
3. Where is population growing fastest as a region?
Sub-Saharan Africa is growing faster than any other world region, with populations in many countries there projected to double between 2022 and 2050, and several, including the Democratic Republic of Congo, Niger, and Somalia, projected to double again between 2024 and 2054.
4. Why is fertility still high in these countries?
High fertility across much of sub-Saharan Africa and parts of South Asia reflects a combination of factors including limited access to family planning, historically high desired family size, lower levels of female education in some areas, and the fact that these regions are earlier in the demographic transition that has already played out in most of Asia, Europe, and the Americas.
5. Which countries will double their populations soonest?
The UN’s 2024 revision specifically identifies Angola, the Central African Republic, the Democratic Republic of Congo, Niger, and Somalia as on track to double their populations between 2024 and 2054, a 30-year timeframe.
6. What is population momentum and why does it matter here?
Population momentum is continued population growth driven by a large existing cohort of young people already moving into their reproductive years, even after fertility per woman starts to fall. It explains why sub-Saharan Africa’s rapid growth is expected to continue for decades even as fertility rates there gradually decline, similar to patterns already observed in Asia and Latin America.
7. Is the United States really among the fastest-growing populous countries?
The US is included among the nine countries expected to contribute most to absolute global population growth, though its growth is driven overwhelmingly by immigration rather than fertility, and its growth rate is far lower than that of the African and South Asian countries on the list; the US recorded a growth rate of just 0.1 percent in 2021, its lowest since the country’s founding.
8. Will Nigeria really overtake the United States in population?
UN projections across multiple recent revisions have consistently shown Nigeria’s population surpassing that of the United States by approximately mid-century, driven by Nigeria’s substantially higher fertility rate and younger age structure compared to the slower-growing, immigration-dependent US population.
9. How many African countries are projected to at least double in population?
UN projections in recent years have identified between 26 and 28 African countries projected to at least double their populations over multi-decade projection windows, with a smaller subset of around 9 to 10 countries projected to increase by a factor of five or more by 2100.
10. Does rapid population growth automatically cause poverty?
Not automatically, but UN officials have noted that population growth concentrated in some of the world’s poorest countries adds a distinct set of challenges to poverty reduction, education, and employment efforts precisely because those countries often have the most limited existing resources and infrastructure to absorb rapidly growing cohorts
Sources
- United Nations Department of Economic and Social Affairs, World Population Prospects 2024: Summary of Results
- United Nations DESA, World Population Prospects: The 2017 Revision, and successive updates on nine-country growth concentration
- United Nations, press coverage of World Population Prospects revisions via Al Jazeera, NBC News, and the Associated Press, 2017-2022
- United Nations DESA Policy Brief No. 167, Leveraging Population Trends for a More Sustainable and Inclusive Future
