The world’s population is projected to hit an estimated 8 billion people on Tuesday, according to a United Nations projection, with much of the growth coming from developing nations in Africa.

Among them is Nigeria, where resources are already stretched to the limit. More than 15 million people in Lagos compete for everything from electricity to light their homes to spots on crowded buses, often for two-hour commutes each way in this sprawling megacity. Some Nigerian children set off for school as early as 5 a.m.

And over the next three decades, the West African nation’s population is expected to soar even more: from 216 million this year to 375 million, the U.N. says. That will make Nigeria the fourth-most populous country in the world after India, China and the United States.

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The upward trend threatens to leave even more people in developing countries further behind, as governments struggle to provide enough classrooms and jobs for a rapidly growing number of youth, and food insecurity becomes an even more urgent problem.

Nigeria is among eight countries the U.N says will account for more than half the world’s population growth between now and 2050 — along with fellow African nations Congo, Ethiopia and Tanzania.

“The population in many countries in sub-Saharan Africa is projected to double between 2022 and 2050, putting additional pressure on already strained resources and challenging policies aimed to reduce poverty and inequalities,” the U.N. report said.

It projected the world’s population will reach around 8.5 billion in 2030, 9.7 billion in 2050 and 10.4 billion in 2100.

Other countries rounding out the list with the fastest growing populations are Egypt, Pakistan, the Philippines and India, which is set to overtake China as the world’s most populous nation next year.

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According to the U.N., the population in sub-Saharan Africa is growing at 2.5% per year — more than three times the global average. Some of that can be attributed to people living longer, but family size remains the driving factor. Women in sub-Saharan Africa on average have 4.6 births, twice the current global average of 2.3.

Families become larger when women start having children early, and 4 out of 10 girls in Africa marry before they turn 18, according to U.N. figures. The rate of teen pregnancy on the continent is the highest in the world — about half of the children born last year to mothers under 20 worldwide were in sub-Saharan Africa.

Still, any effort to reduce family size now would come too late to significantly slow the 2050 growth projections, the U.N. said. About two-thirds of it “will be driven by the momentum of past growth.”

“Such growth would occur even if childbearing in today’s high-fertility countries were to fall immediately to around two births per woman,” the report found.

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Politics also have played a role in Tanzania, where former President John Magufuli, who ruled the East African country from 2015 until his death in 2021, discouraged birth control, saying that a large population was good for the economy.

He opposed family planning programs promoted by outside groups, and in a 2019 speech urged women not to “block ovaries.” He even described users of contraceptives as “lazy” in a country he said was awash with cheap food. {snip}

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