The demographic trajectory of the world’s most populous nations is set for a dramatic transformation in the coming decades, with significant shifts in rankings, peaking populations, and in some cases, steep declines by the end of the century. Projections from leading sources, including the United Nations (UN) and a landmark study by the Institute for Health Metrics and Evaluation (IHME) published in The Lancet, paint a picture of a world where population growth slows and is unevenly distributed, leading to profound social, economic, and geopolitical realignments.
While the UN and IHME models offer different potential futures based on varying assumptions about fertility, mortality, and migration, both foresee a world where India remains a population behemoth, African nations rise in prominence, and once-dominant China sees a significant reduction in its populace.
Here is a consolidated view of population projections for the current ten most populous countries at key milestones in the 21st century.
Population Projections of the World’s Current 10 Largest Countries (in millions)
| Rank (2025) | Country | Est. Population 2025 | Projected Population 2030 | Projected Population 2050 | Projected Population 2100 | Key Projections & Insights |
| 1 | India | 1,464 | 1,515 | 1,670 (UN) / 1,610 (IHME peak ~2048) | 1,530 (UN) / 1,090 (IHME) | According to the UN, India will remain the world’s most populous country through 2100. The Lancet/IHME study projects an earlier peak around mid-century followed by a sharp decline. |
| 2 | China | 1,416 | 1,416 | 1,317 (UN) / 1,070 (IHME) | 771 (UN) / 732 (IHME) | Both models project a significant and continuous population decline for China, with the IHME forecasting a more rapid decrease of nearly 50% from its current population by 2100. |
| 3 | United States | 347 | 352 | 375 (UN) | 394 (UN) / 336 (IHME) | The U.S. is expected to see continued, albeit slow, population growth, largely sustained by immigration. It is projected to remain among the top five most populous nations. |
| 4 | Indonesia | 286 | 294 | 317 (UN) | 297 (UN) | Indonesia’s population is projected to continue growing until around mid-century before beginning a gradual decline. |
| 5 | Pakistan | 255 | 274 | 366 (UN) | 487 (UN) / 248 (IHME) | Projections for Pakistan vary significantly. The UN foresees continued strong growth, making it the fourth most populous country by 2100, while the IHME model suggests a stabilization and potential decline. |
| 6 | Nigeria | 238 | 263 | 375 (UN) | 546 (UN) / 791 (IHME) | Nigeria is on a path of rapid and sustained population growth, with both models agreeing it will become one of the world’s most populous countries, ranking as high as second globally by 2100 according to IHME. |
| 7 | Brazil | 213 | 216 | 231 (UN) | 181 (UN) | Brazil’s population is expected to peak in the coming decades and then enter a period of decline through the end of the century. |
| 8 | Bangladesh | 176 | 182 | 204 (UN) | 177 (UN) | The population of Bangladesh is projected to grow until around 2060, after which it is expected to start declining. |
| 9 | Russia | 144 | 143 | 133 (UN) | 112 (UN) | Russia is facing a consistent demographic decline, with its population projected to be significantly smaller by the end of the century. |
| 10 | Mexico | 132 | 135 | 144 (UN) | 116 (UN) | Mexico’s population is projected to continue growing for the next few decades before it begins to decline. |
Note: Population figures are rounded and compiled from the UN’s “World Population Prospects” and the IHME study published in The Lancet. Projections can vary based on the methodologies and underlying assumptions of the respective studies.
Shifting Global Power Dynamics
By 2100, the list of the world’s most populous countries is expected to look considerably different. While India is projected to hold the top spot, several African nations are forecast to enter the top 10, including the Democratic Republic of the Congo and Ethiopia, driven by higher fertility rates. Conversely, countries with rapidly aging populations and low fertility rates, such as China and many European nations, will see their global population rankings fall.
These demographic shifts carry significant implications for everything from economic growth and resource management to geopolitical influence and environmental sustainability. The world is on the brink of a new demographic era, one that will redefine national and global priorities for generations to come.