For most of the time that humans have existed, our ranks have grown really, really slowly. There were an estimated 4 million people on Earth in 10,000 B.C., and after the following 10 millennia, the planetwide population had only reached 190 million. Even in 1800, the total number of humans was still under 1 billion.
The climb since then—made possible by advances in medicine, sanitation, and food production—has been astounding. By 1900, there were 1.65 billion people; by 2000, there were more than 6 billion. Just two decades later, the global population sits at 7.7 billion.
But soon—or at least, soon in the context of human history—the number of people on Earth will stop growing. Based on the latest figures from the United Nations, demographers’ best guess for when this will happen is about 2100. By then, the global population is projected to have risen to just shy of 11 billion.
Humanity has experienced population drop-offs before—the Black Death is thought to have killed about 200 million people—but this time will be different. “In the past, when the world population experienced a decline,” Tom Vogl, a development economist at UC San Diego, told me, “it was because a lot of people died.” This coming transition, meanwhile, will be the result of people having fewer kids—a product of rising incomes and levels of education, especially for women and especially in less-wealthy countries.
There’s always some uncertainty to making predictions, but Vogl said that population projections are usually “less uncertain” than other social and economic projections. This is because researchers already know roughly how many humans there are now, as well as how old everyone is, so they ca ..
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