Top 25 Most Populous Countries in the World

The world is a populous place (7.6 billion people as of mid-2017) and ever-growing. Even as some regions of the world grow slowly or are even shrinking (the more developed economies), other regions of the world are growing quickly (the least-developed nations). Add in the fact that people live longer due to improvements in medicine and infrastructure (such as sanitation and water treatment), and Earth is expected to see an increase in population for decades to come. It's slower growth than in decades past but still going up.

Population and Measures of Fertility

One measure used to forecast population growth is based on the fertility of a nation or the size of families that people have. Replacement level fertility of a population is considered 2.1 children born to every woman in a country. If a nation has a 2.1 fertility rate, it is not growing at all, just replacing the people that it already has. In highly developed industrial economies, especially those where there are more aged and elderly people than young people, the fertility rate is near the replacement level or below.

Part of the reason why developed economies have lower fertility is that women there have more opportunities to contribute to the economy and put off childbearing until later, after higher education and entry into the workforce. Women in developed economies also have fewer pregnancies during their teen years.

The world overall fertility rate is 2.5; in the 1960s, it was around double that. In the 25 fastest-growing countries, the fertility rate is 4.7 to 7.2 births per woman, according to World Bank data. Percentage-wise, the world is growing about 1.1% per year or 83 million people. The United Nations projects the world will have 8.6 billion by 2030 and 11.2 billion in 2100, though the growth rate has been slowing for decades.

Where Population Is Growing

The most populous area of the world is Asia, as it's home to three of the top four and half of the top 10 most populated nations (placing Russia in Europe). Sixty percent of the world's people live in Asia, or about 4.5 billion.

More than half of the expected population growth of 2.2 billion people by 2050 will be in Africa (1.3 billion), and Asia will likely be the No. 2 contributor to the world population growth. India is growing more quickly than China (which is projected to be relatively stable until 2030 and then fall slightly thereafter) and likely will take over the No. 1 spot on the list after 2024, when both countries are expected to have 1.44 billion people.

Elsewhere on the planet, growth is forecast to be more modest, closer to 1% than 2%. Africa's increase in population over the coming decades will be due to high fertility rates there. Nigeria is poised to take over the No. 3 location on the most populous countries list by 2030, as each woman there has 5.5 children in her family.

Population growth is expected to be high in the least-developed nations of the world. Of the 47 least-developed countries, 33 are in Africa. The UN expects this large amount of growth in the poorest countries to strain these countries' ability to care for the poor, fight hunger, expand education and health care, and provide other basic services.

Where Population Is Shrinking 

The UN's projections for 2050 show only one region actually decreasing in population, Europe, especially some countries in eastern Europe, where numbers could fall more than 15%. The United States' population is projected to fall as well when based on UN fertility projections, but longer life expectancies and immigration keep the population on the rise slightly in forecasts, according to Pew Research. The UN noted in its 2017 report:

"The ten most populous countries with below replacement fertility are China, the United States of America, Brazil, the Russian Federation, Japan, Viet Nam, Germany, the Islamic Republic of Iran, Thailand, and the United Kingdom (in order of population size)." 

Most Populous Countries

These nations each have a population of more than 55 million and together represent about 75% of the world's residents. The data are estimates from mid-2017:

1. China: 1,410,000,000
2. India: 1,339,000,000
3. United States: 324,000,000
4. Indonesia: 264,000,000
5. Brazil: 209,000,000
6. Pakistan: 197,000,000
7. Nigeria: 191,000,000
8. Bangladesh: 165,000,000
9. Russia: 144,000,000
10. Mexico: 129,000,000
11. Japan: 127,000,000
12. Ethiopia: 105,000,000
13. Philippines: 105,000,000
14. Egypt: 98,000,000
15. Vietnam: 96,000,000
16. Germany: 82,000,000
17. Democratic Republic of the Congo: 81,000,000
18. Iran: 81,000,000
19. Turkey: 81,000,000
20. Thailand: 69,000,000
21. United Kingdom: 62,000,000
22. France: 65,000,000
23. Italy: 59,000,000
24. Tanzania: 57,000,000
25. South Africa: 57,000,000

Source

• United Nations Population Division World Population Prospects