The end of this century will bring sweeping shifts in how populations are distributed worldwide. In the scenario many scientists project, China will no longer be the most populous nation, with India taking that spot. Congo and other African nations are expected to see substantial population growth, while countries like Spain could lose about half of their inhabitants, settling around 23 million from today’s roughly 46 million. These trends, echoed across multiple studies that use the same criteria, suggest an initial rise in population followed by a gradual global decline over the coming decades.
Environmentally, this overall reduction could lower planetary pressures, yet it will also pose new challenges: how to support an aging population while dealing with a shrinking workforce. In total, estimates point to a peak global population of about 9.7 billion in 2064, then a gradual decline to around 8.8 billion by century’s end. This shift is linked to better access to education for women and broader use of birth control, a consensus supported by the Lancet and corroborated by subsequent researchers in the years that followed.
The planet will experience major demographic changes verified by demographic researchers.
By 2100, new analyses from researchers at the Institute for Health Metrics and Evaluation at Washington University describe a world where 183 of 195 countries will not have fertility rates high enough to maintain their current populations. A regional map illustrates how population levels will diverge from country to country.
Some 23 countries, including Japan, Thailand, Italy, and Spain, are projected to see population declines greater than 50 percent according to these researchers.
It will fall to half of China’s population
Sub-Saharan Africa is projected to triple in size over the same period, which could yield a striking outcome: by the century’s end, nearly half of the world’s people might live in Africa.
The Lancet report also notes a sharp drop in the global working-age population that could hamper economic growth in nations such as China, with potential negative implications for labor markets and welfare systems. In fact, China is expected to lose its status as the most populous country, with a population around 732 million—a far cry from today’s 1.4 billion.
Some of the most populous nations in 2100 are highlighted in Lancet’s projections.
Immigration could help countries facing low fertility by offsetting declines, potentially stabilizing population sizes in the United States, Australia, Canada, and similar nations that welcome newcomers.
Christopher Murray, who led the study, told CNN that while the world focused on past baby booms, it is suddenly approaching a tipping point. “We are rapidly moving from the problem of too many people to the problem of too few people,” he said.
Population decline in Europe and Asia
By 2100, Asia and Eastern and Central Europe are expected to experience the fastest population declines.
Projections show Japan dropping from about 128 million in 2017 to around 60 million in 2100, and Thailand from 71 to 35 million. Spain could fall from 46 million to 23 million, Italy from 61 to 31 million, Portugal from 11 to 5 million, and South Korea from 53 to 27 million. In addition, roughly 34 other countries, including China, are projected to see declines of up to 50 percent.
The trend is not only about fewer people, but about aging societies. The report notes that economic growth could be hindered as the number of retirees rises while the pool of working-age people shrinks.
Sub-Saharan Africa’s boom
Researchers anticipate Sub-Saharan Africa could grow from about 1.03 billion in 2017 to 3.07 billion by 2100. North Africa and the Middle East are the only other major region expected to surpass their 2017 population, rising to around 978 million from 600 million.
As fertility remains higher for longer, the relative share of Africans in the world population is expected to rise sharply. The projection suggests that, by century’s end, roughly half of humanity could live in Africa.
The world aging trend
The study also forecasts notable shifts in age structure as fertility falls and life expectancy rises. Globally, about 2.37 billion people older than 65 are projected to exist in 2100, compared with 1.7 billion under age 20. The total number of people over 80 could increase sixfold, from 141 million to 866 million, while the number of children under five might fall by more than 40 percent from 681 million in 2017 to 401 million in 2100.
These dramatic changes in the number of working-age people will affect economies and the balance of power across the world.
Migration as a counterbalance
The report authors caution that immigration can offset demographic decline. Countries with open immigration policies may be better positioned to maintain population size and sustain economic growth as fertility declines.
Murray notes that if birth rates fall faster than deaths rise, migration becomes essential to prevent a shrinking population. Even as environmental and climate factors shift, an aging population will continue to shape social and economic policies.
The analysis highlights the substantial challenges a shrinking workforce will pose to growth and the heavier burden on health and social support systems as the population ages.
The role of migration is underscored: it can help stabilize populations and support economies when fertility declines. The key question remains how societies organize themselves and adapt to these new demographic realities as they evolve.
References to the Lancet study and related research provide the foundation for these projections and offer a framework for policymakers to plan for an aging, migratory, and globally connected world.
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