Population shifts and aging across the globe
The coming century will bring bold changes in how people live and where they are. In the near future, India is expected to surpass China as the most populous nation. Africa, led by countries like the Congo, will see rapid population growth, while places such as Spain may lose a significant portion of their inhabitants, shrinking toward the mid-20s of millions. These trends appear consistently across multiple studies that use the same criteria. After a period of growth, humanity is projected to enter a long phase of gradual decline.
From an environmental standpoint, the overall footprint of humanity is forecast to ease as populations shrink. Yet new challenges will surface, especially around how to sustain a growing number of older adults while a shrinking workforce is expected to support them.
On balance, the world population is projected to peak around 9.7 billion in 2064 and then trend downward toward roughly 8.8 billion by the end of the century. This pattern aligns with findings that increased access to education and family planning is driving lower birth rates, a view confirmed by several researchers in the Lancet and subsequently by other teams of scientists.
By 2100, most of the world’s countries will not have the fertility needed to sustain current population levels, according to researchers from the Institute for Health Metrics and Evaluation at Washington University School of Medicine. A chart highlights how population will differ by country.
Twenty three nations including Japan, Thailand, Italy, and Spain are expected to see declines exceeding half of their current populations, according to these studies.
It will fall to half of China’s population
Sub-Saharan Africa could see its population triple over the century, potentially reshaping global demographics so that by the century’s end nearly half of all people in the world reside in Africa.
The Lancet study also notes a sharp drop in the working-age group, which could slow economic growth in countries such as China and affect welfare systems. By century’s end China may be home to about 732 million people, far below today’s level of around 1.4 billion.
Immigration may help offset the decline in birth rates in nations with low fertility, offering a path to stabilize population and support economies. This is especially relevant for the United States, Australia, and Canada.
As researchers noted, the world has long expected a baby boom since the 1960s. The shift toward slower growth or population decline marks a tipping point as societies adapt to changes in birth patterns.
Population decline in Europe and Asia
Across 2100, the sharpest drops are forecast for Asia and Eastern and Central Europe.
Estimates show Japan shrinking from about 128 million today to roughly 60 million by 2100, while Thailand could fall from 71 to 35 million. Spain might drop from 46 to 23 million, Italy from 61 to 31 million, Portugal from 11 to 5 million, and South Korea from 53 to 27 million. In many other countries, populations may fall by as much as half.
Beyond numbers, the aging trend is clear. Fewer births coupled with longer lives will tilt the age balance, placing more people in need of government services while fewer contribute taxes, a dynamic that could dampen economic momentum.
Africa trains ahead
Sub-Saharan Africa is projected to experience a substantial rise, growing from about 1.03 billion in 2017 to around 3.07 billion in 2100. North Africa and the Middle East stands as the other region likely to increase, reaching about 978 million.
Because fertility remains high for longer, Africa’s share of the world population would rise. In the scenario outlined, by the end of the century almost half of humanity could be African.
The world grows older
Experts also anticipate a major shift in the global age structure as fertility falls and longevity rises. By 2100 the world could see 2.37 billion people aged 65 and over, compared with about 1.7 billion under 20. The number of people over 80 could multiply sixfold, while the under-5 group might shrink by more than 40 percent, to around 401 million.
These large changes in working-age populations in countries such as India and China would slow economic growth and prompt adjustments in how societies organize and fund programs like health care and retirement support.
The role of migration
Researchers stress that immigration could offset some of the decline from lower birth rates. Countries with open immigration policies may better maintain population size and sustain economic activity as fertility drops.
The authors note that while lower population growth could bring environmental and climate benefits, an aging society will still pose challenges. The key task is finding practical ways to adapt to a shift in how economies are structured and how social support is financed.
Note: original study details are published in Lancet, with further analyses by multiple teams and institutions.
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