These countries will have the largest populations - by the end of the century 

The World Population in 2100, by Country

In 2015, the United Nations predicted that the global population could surpass 11 billion by the end of the century.

Last year, the UN revised these estimates, but the numbers it came up with were still well above 10 billion. These regular projections from the UN have been the status quo—until now.

Plenty of signs have pointed to there being a population plateau, but recent research from the Institute for Health Metrics and Evaluation (IHME), published in The Lancet, suggests that the number of people on this planet may actually start to shrink well before the year 2100.

Here’s a closer look at these complex projections.

UN vs. IHME Population Estimates

According to the UN, the world population is set to steadily rise over the years:

2030: 8.5 billion

2050: 9.7 billion

2100: 10.9 billion

In contrast, IHME paints a different picture. It projects the population to actually peak at 9.7 billion in 2064. Following this trajectory, there could be 8.8 billion people in 2100, approximately 2 billion fewer than previously thought.

Various demographic factors are behind these differences—higher life expectancies, migration rates, and lower fertility rates. For this last factor, independent drivers including contraceptive access and higher educational attainment were also considered.

A shifting age structure is also a key aspect of this transition. By 2100, over a quarter of the world or nearly 2.37 billion will be aged 65 years and above.

The Most Populous Countries in 2100

Amid all these demographic sea changes, which countries will come out on top?

Despite an overall decline in numbers to 1.09 billion people in 2100, India moves up from second to first place on the population leaderboard.

The populations of both India and China will begin to contract after the mid-century—and it’s predicted that China’s total population will drop by almost half to 732 million by 2100.

Led by Nigeria, Sub-Saharan Africa is the only region that will continue to see growth by century’s end. In fact, four of the top 10 countries in the world in terms of population count will be located in Sub-Saharan Africa.

Tightly Packed Together

One final thing to consider is how population density may look in 2100, with many more people clustered in the same areas. For example, Nigeria is dealing with a land area nearly 11 times smaller than the U.S.—but it will have more than double the population.

Regardless of how the future population count shakes out, it’s clear that these heavyweight countries will undergo significant transformation in the coming decades.