World population projections are estimates of the future size, growth, and distribution of the human population, based on assumptions about fertility, mortality, and migration. World population projections are useful for understanding the past, present, and future trends of the population, as well as for planning and policymaking in various fields, such as health, education, environment, and development.
One of the main sources of world population projections is the United Nations, which publishes the World Population Prospects every two years. The latest edition, the 2022 revision, presents population estimates from 1950 to 2021, and population projections from 2021 to 2100, for 237 countries and regions, and for the world as a whole. The projections are based on three scenarios: low, medium, and high fertility, which reflect different assumptions about the future levels and trends of fertility in each country and region.
According to the medium-fertility scenario, which is the most widely used and cited, the world population is projected to increase from 7.9 billion in 2021 to 9.7 billion in 2050, and to 10.9 billion in 2100. This means that the world population will grow by 22% between 2021 and 2050, and by 38% between 2021 and 2100. However, the growth rate of the world population will slow down over time, from 1.0% per year in 2021-2025, to 0.5% per year in 2045-2050, and to 0.1% per year in 2095-2100.
The world population growth will also vary by region and by country. Some regions and countries will experience faster or slower growth, or even decline, depending on their fertility, mortality, and migration patterns. The following table shows the projected population size and growth rate of the major regions of the world in 2021, 2050, and 2100, according to the medium-fertility scenario:
| Region | Population (millions) | Growth rate (% per year) |
| | 2021 | 2050 | 2100 | 2021-2050 | 2050-2100 |
| World | 7,874 | 9,735 | 10,875 | 0.8 | 0.3 |
| Africa | 1,373 | 2,489 | 3,775 | 2.5 | 1.3 |
| Asia | 4,678 | 5,267 | 5,096 | 0.4 | -0.1 |
| Europe | 748 | 710 | 603 | -0.2 | -0.5 |
| Latin America and the Caribbean | 653 | 769 | 768 | 0.6 | 0.0 |
| Northern America | 368 | 435 | 500 | 0.6 | 0.4 |
| Oceania | 43 | 66 | 83 | 1.5 | 0.7 |
The table shows that Africa will be the fastest-growing region in the world, with its population more than doubling by 2050, and nearly tripling by 2100. Asia will remain the largest region in the world, but its population will peak around 2050, and then decline slightly by 2100. Europe will be the only region to experience a population decline by 2050, and will continue to shrink by 2100. Latin America and the Caribbean will have a moderate population growth by 2050, but will stabilize by 2100. Northern America and Oceania will have a steady population growth throughout the century.
The table also shows that the world population will become more concentrated in Africa and Asia, which will account for 86% of the world population by 2100, up from 77% in 2021. Europe and Latin America and the Caribbean will see their shares of the world population decline, from 10% and 8% in 2021, to 6% and 7% in 2100, respectively. Northern America and Oceania will maintain their shares of the world population, at 5% and 1%, respectively.
World population projections also provide information about the age structure and composition of the population, which are important indicators of the demographic and social characteristics of a population. The age structure of a population refers to the distribution of the population by age groups, such as children, working-age adults, and elderly. The age composition of a population refers to the proportion of the population in each age group, such as the child dependency ratio, the old-age dependency ratio, and the median age.
The age structure and composition of the world population will change significantly over time, as a result of the changes in fertility, mortality, and migration. The following table shows the projected age composition of the world population in 2021, 2050, and 2100, according to the medium-fertility scenario:
| Age group | Population (millions) | Proportion (%) |
| | 2021 | 2050 | 2100 | 2021 | 2050 | 2100 |
| 0-14 | 1,907 | 2,015 | 2,015 | 24.2 | 20.7 | 18.5 |
| 15-64 | 5,270 | 6,125 | 6,303 | 66.9 | 62.9 | 57.9 |
| 65+ | 697 | 1,595 | 2,557 | 8.9 | 16.4 | 23.5 |
| Child dependency ratio | 36.2 | 32.9 | 32.0 | | | |
| Old-age dependency ratio | 13.2 | 26.0 | 40.6 | | | |
| Median age | 31.0 | 36.6 | 42.6 | | | |
The table shows that the world population will age over time, as the proportion of children will decline, and the proportion of elderly will increase. The child dependency ratio, which measures the number of children under 15 per 100 working-age adults, will decrease from 36.2 in 2021, to 32.9 in 2050, and to 32.0 in 2100. The old-age dependency ratio, which measures the number of elderly over 65 per 100 working-age adults, will increase from 13.2 in 2021, to 26.0 in 2050, and to 40.6 in 2100. The median age, which measures the age at which half of the population is older and half is younger, will increase from 31.0 in 2021, to 36.6 in 2050, and to 42.6 in 2100.
The aging of the world population will have various implications for the social and economic development of the world, such as the demand for health care, pensions, and social services, the supply of labor and human capital, and the potential for innovation and productivity. The aging of the world population will also vary by region and by country, depending on their demographic trajectories and policies. Some regions and countries will face more challenges and opportunities than others, as they cope with the changing age structure and composition of their populations.
In conclusion, world population projections are valuable tools for understanding and anticipating the future of the human population, as well as for informing and guiding the actions and decisions of various stakeholders, such as governments, international organizations, civil society, and individuals. World population projections are based on assumptions and uncertainties, and are subject to revisions and updates, as new data and information become available. World population projections are not predictions or forecasts, but scenarios and possibilities, that reflect the potential outcomes of the demographic trends and transitions of the world population.
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