The world’s population of about 8 billion is expected to reach 10.4 billion by 2100, a growth largely driven by a phenomenon called “population momentum.” Population momentum occurs when a large generation of young people in their reproductive years leads to the number of births exceeding the number of deaths.
Given that momentum, there is very little that policies or family planning can do to curb population growth for the next several decades, said John Bongaarts, a distinguished scholar at the Population Council, a nonprofit that conducts demographic research on underserved populations.
“You have very large numbers of young people, and these young people have to go through reproductive years, which takes 40 to 50 years,” Bongaarts said. “Then you have the children of these children, so momentum actually takes more than three decades to run its course. Maybe 60 to 70 years.”
That would be good news for affluent countries that are grappling with record-low fertility rates, aging populations, and shrinking workforces. In the United States, people aged 65 and older are projected by 2034 to outnumber those under the age of 18 for the first time in U.S. history. China recorded its first population decline in decades this January, and an aging population has already put an expiration date on its economic miracle. South Korea is desperately looking for ways to raise its fertility rate, currently the world’s lowest at 0.78 births per woman. A fertility rate of 2.1 is needed for a country to maintain a stable population without migration.
But instead, half of the global population growth from 2022 to 2050 will occur in sub-Saharan Africa. The region’s population is currently growing three times faster than the rest of the world, and by the end of the century, it will be home to a third of all people in the world, compared to only 14 percent in 2019. This means that the burden of rapid population growth will fall on some of the poorest countries in the world, with nearly half of the region having a gross national income per capita below $1,135, and in places that are among the most vulnerable to climate change.
Fertility rates are declining in sub-Saharan Africa, but not enough to avoid concerns over food security, adequate infrastructure, and employment for the influx of young people. Sub-Saharan Africa has a fertility rate of 4.45, and Niger, Chad, Somalia, and the Democratic Republic of the Congo lead the region with rates exceeding 6.0. By comparison, the United States and Western Europe have rates around 1.6. Experts say that part of the explanation can be found in a mindset ingrained from times of turmoil and war in African history: strength in numbers.
The sentiment prevails at the family level, particularly in poor families that consider having many children to be a safety net and too few children to be a gamble, said Parfait Eloundou-Enyegue, a global development professor at Cornell University.
“There’s still a cultural tradition and expectation that within a family, if you just have one person who succeeds, then they [could] lift everybody up,” said Eloundou-Enyegue, who grew up in Cameroon. “From that perspective, if you are in a relatively poor household, you may have many kids, and just by chance one of them can make it, and that one person is going to rescue the rest of the family.”
One way to bend the population curve is by increasing family planning and contraceptive use. Malawi has emerged as a front-runner in family planning and has significantly improved access to contraception, with a contraceptive use rate of 58 percent. That’s about double the rate in the rest of sub-Saharan Africa and close to the U.S. rate of 65 percent.
But intrauterine devices cost up to $400 in other parts of Africa, and some governments are not willing to adopt family planning programs, making increasing contraceptive use a tall order. Refusal to accept family planning assistance from Western nations also stems from a deep distrust rooted in a history of Western colonization and exploitation.
In “the country of Benin … they are really looking into what is best for the country in terms of shifting the public attitudes [of family planning], but they want to make this a very Indigenous effort, one that is not really influenced by external viewpoints,” Eloundou-Enyegue said.
Governments also underestimate the population momentum effect and instead prioritize large populations, which remain important for countries such as Nigeria, where national revenue is allocated to each of its 36 states based on population size.
Another way to speed up the fertility decline is in the classroom. Numerous studies have associated lower fertility with more schooling for women; one study from IZA World Labor found that an increase in women’s schooling—from half of the schooling men receive to all of what men receive—is associated with a fertility rate decline from 6.0 to 2.0, based on data from 146 countries. More education means later marriage, later and fewer childbirths, and more awareness about sexual and reproductive health, demographer Anne Goujon said.
“With more schooling, women are empowered and likely to pursue a career,” Goujon, the director of the Population and Just Societies Program at the International Institute for Applied Systems Analysis, added.
The problem is that school is out. Sub-Saharan Africa’s education exclusion rate is among the highest in the world, with more than 20 percent of primary-age children and almost 60 percent of youth between the ages of 15 to 17 out of school, according to the World Bank. And no country in the region has reached gender parity in both primary and secondary education, according to UNESCO.
The Adolescent Girls Initiative for Learning and Empowerment (AGILE), a World Bank initiative in Nigeria, is working to bring more girls into classrooms and has built more than 5,000 classrooms in both existing and new schools. More than 600,000 girls have started receiving a secondary education since the project started in 2020.
But the fight for gender parity is not just about building more infrastructure but also tearing down the “deep-rooted societal beliefs” that reinforce traditional gender roles and limit girls to domestic and marriage duties, AGILE task team leader Aisha Garba Mohammed said.
“Girls’ education is hindered by the gendered division of household labor, with girls often expected to contribute to providing care for younger siblings or engaging in farming activities, limiting their time and availability to attend school,” she said.
Encouraging girls to enter and stay in school is also marred by the prevalence of gender-based violence that can even occur during their long journeys to get to schools, which are often few and far between. In 2014, a jihadi militant group abducted 276 students from an all-girls secondary school in the village of Chibok in Nigeria; nearly 100 are still missing.
“In many parts of Africa, female students have been directly targeted, abducted, and kidnapped, such as the case of [the] Chibok girls in Borno,” Mohammed said. “As such, families are increasingly reluctant to send their girls to school.”
As programs such as AGILE help bring more girls into classrooms and schools begin to adopt and enforce guidelines related to gender-based violence, sub-Saharan Africa may expect to see “an acceleration of the fertility decline as the subsequent better-educated cohorts of women move into the main childbearing ages,” according to Goujoun.
If sub-Saharan Africa can accelerate its fertility decline, there will be proportionally more adults in the population, increasing productivity and driving economic growth. Demographers call this phenomenon the “demographic dividend,” where lower fertility leads to economic growth, which allows parents to invest more in fewer children.
“It establishes norms of parenting and investing in kids that are going to stay in the next generation,” Eloundou-Enyegue said. “Once people get accustomed to providing education to kids, sending them to the best schools, the price and quality of education rises, and there’s no turning back.”
The problem with the demographic dividend is exactly that: There is no turning back, and nowhere is that more noticeable than in South Korea. The South Korean government has spent more than $200 billion in the past 16 years to expand child care and support new mothers, only to watch the fertility rate drop more than 25 percent. Young people value their education and careers, and with such a high cost of living in Seoul where nearly one out of five South Koreans live, having kids is the last thing on many young South Korean couples’ minds.
“Just as much as we were initially interested in pushing education, we have to find a way to make home production rewarding, meaning raising children should be a valued activity [in South Korea],” Eloundou-Enyegue said.
With more mouths to feed and jobs to find, rapid population growth presents a growing strain on food and infrastructure, an oversaturated job market with skyrocketing unemployment, and a weaker capacity for poor communities to adapt to climate change. Communities in sub-Saharan Africa are some of the most vulnerable to climate change despite being some of the world’s lowest carbon dioxide emitters.
Climate change may make it even harder to feed those extra billions, and indeed, declining crop yields mean that some of the population projections may not actually even materialize. Patrick Gerland, the chief of the population estimates and projections section of the U.N. population division, noted that the U.N. global population projections do not explicitly take into account external factors such as food insecurity and climate change.
“[The U.N. doesn’t] take into account the effects of climate change or rising food prices, and part of the reason for that is that the international community typically reacts vigorously when you see tens of millions of people dying,” said Bongaarts, the Population Council scholar.
So while mass starvation is unlikely, even with another big population boom and rising food prices, unchecked population growth will be “disastrous” for young people facing an overly saturated job market and mass unemployment, Bongaarts said.
And with more mouths to feed and fewer jobs to feed them, inequality is only going to get worse, said Eloundou-Enyegue.
“People at the very top [in sub-Saharan Africa] live just as comfortably, lavishly as they would in any major city in the world. At the other end of the spectrum, you’re going to have major urban slums where you have concentrations of people living in poverty,” he said. “The epicenter of inequality is shifting to Africa.”