Even more people than we thought—many millions more. That’s the headline from the United Nations’ latest population projections. By 2100, there could be almost 11 billion humans walking the Earth.
In 2011, the U.N. estimated 10.1 billion people by century’s end. It has now raised that by 8%, or 800 million people. That’s mainly because it doesn’t see fertility rates in fast-growing countries slowing as soon as it thought. Mothers in 15 sub-Saharan Africa countries will have 5% more kids, for example.
Fertility rates will vary widely depending on the continent. Europe will struggle to hit replacement level (its population will decline 14%). But Africa will almost quadruple in size: from 1.1 billion now, to 4.2 billion by 2100. Eight of the 10 biggest growers are on the African continent, with Nigeria leading the way. Its population is projected to increase by a staggering 730 million people, from 184 to 914 million.
That would make Nigeria a more populous country than the United States. But the U.S. is an exception in the rich world, in population terms. It is expected to add 146 million people, to reach 462 million in 2100. India rounds out the top 10: It will be the world’s largest country by 2028. The U.N. predicts it will have up to 1.6 billion people; by contrast, China will start declining after 2030.
Indonesia, Tanzania, Pakistan, the D.R. Congo, Ethiopia, Uganda, and Niger will all have 200-million-plus populations by 2100. Life expectancy will improve in "least developed countries" from 58 years in 2010, to 70 by 2050, and 78 by 2100. Meanwhile, the developed world will continue to get older. By 2050, European countries, for example, will have double the amount of older people to children (32% to 16%).
It’s important to note that the projections are just that, and there’s a lot of leeway built in. Depending on fertility rates, 2100's world population could be anything from 7 billion (roughly what it is now) to almost 17 billion, according to the U.N.'s figures. Other estimates put the range at 9 to 13 billion.