The global fertility rate will gradually decline from now through 2100, continuing a trend since 1950, driven largely by female educational attainment and contraception access, according to newly published projections from the Institute for Health Metrics and Evaluation (IHME). Accompanying that decline will be dramatic shifts in the distribution of births throughout the world, with the majority of children being born in some of the poorest parts of the world.

“By the end of the century, over three-quarters of global births will happen in low- and lower-middle income countries, which also happen to be places that are going to be under heat stress and vulnerable conditions—food insecurities, economic challenges, environmental challenges—all piling up on top of having still-high fertility rates,” says Natalia Bhattacharjee, an IHME researcher and colead author of the study. High-income countries, meanwhile, will face other challenges, such as maintaining their workforce and managing an aging population’s health care and social security.

“We want to bring these trends to the attention of national governments so they can plan for emerging problems in the economy, environment, and geopolitical securities that should be addressed,” Bhattacharjee says. The projections are an opportunity to give people “a chance to see what the future would probably look like.”

What They Found 

The world’s total fertility rate has more than halved since 1950, falling from 4.8 children per childbearing person then to about 2.2 today across 204 countries and territories. That’s just barely above a stabilizing population replacement rate of 2.1,

The researchers predict that the rate will continue to decline to 1.8 in 2050, when roughly a quarter of the world’s countries will have fertility rates higher than the replacement rate, and then to 1.6 in 2100, when only six countries will.

Everyone  will have full access to contraception by 2030; “pro-natal” policies are enacted to create supportive environments for those giving birth; and all three of these are achieved. Examples of pro-natal policies include childcare subsidies, extended parental leave, broader access to infertility treatment, and other forms of support for childcare. Even in the scenario when all three of these occur, however, the global fertility rate would still decline to 1.6 by 2100.

“These fertility trends have very far-reaching implications, from economic, climate change, and labor force points of view,” says Randi Goldman, an OB/GYN and program director of the Reproductive Endocrinology and Infertility Fellowship at the Zucker School of Medicine at Hofstra/Northwell in New York. “It’s going to be really critical that we have well-informed proactive policymakers who can address some of the upcoming challenges that come from this change in the global fertility rate.”

More than half the world’s population will be born in sub-Saharan Africa by 2100, with just 1 in 10 children born in what are high-income countries today. On the one hand, the falling fertility rate could help reduce carbon emissions and “alleviate some strain on global food systems, fragile environments, and other finite resources,” the study authors write. At the same time, however, most children will be born in parts of the world with the least health-care infrastructure and “most vulnerable to climate change, resource insecurity, political instability, poverty, and child mortality.”

The potential silver lining of the decline is that fewer people use fewer resources. Nonetheless, Goldman says, “I’m not sure those benefits are going to offset the risks having lower fertility rates worldwide with all the other implications.”

In today’s high-income countries, the shrinking fertility rate will mean a shrinking labor force, with fewer working-age adults available to support a larger aging population that will be living longer. Policymakers will therefore need to plan for the increased pressure on health insurance, social security, and health-care infrastructure, the study authors note.

Better and more open immigration policies can be part of the solution for high-income countries, Bhattacharjee says. Immigration, though, is also a very complicated potential solution, Goldman adds. Immigration policies to address future low-fertility challenges should be implemented thoughtfully and ethically, she says, both in terms of nonexploitative policies concerning the immigrants and given the risk of brain drain.

Perhaps the biggest demographic shift will be the anticipated explosion of births in sub-Saharan Africa. Births there currently account for nearly 30% of the world’s population today, but are expected to increase to more than half (54%) in 2100. Even then, however, the overall fertility rate of sub-Saharan Africa will likely fall below replacement levels at about 1.8 per childbearing person.

Making Sense of Falling Fertility :  The authors caution that their prediction of declining global fertility “should not be used to justify more draconian measures that limit reproductive rights,” such as restricting access to contraception or abortion, both because these are fundamental rights that should be available to all people and because of the negative impacts such restrictions have on individuals and society as a whole. They point to the example of Romania in the 1960s through the 1980s, when severe restrictions on contraception and abortion resulted in high maternal mortality rates, growth in orphanage populations, and long-term harmful effects on overall educational outcomes and the labor market.

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