The world’s population is getting older, slowing down and may stop growing completely by 2100.
Women are having fewer babies, the number of elders is rising fast and an increased number of countries face population declines, according to a projection of world population trends released Monday by the United Nations.
The global population of 7.7 billion will increase to 9.7 billion by midcentury and may peak at 10.9 billion by around 2100, the United Nations said. The findings are a downward revision from the previous forecast by the global body, when it projected 11.2 billion people would inhabit the planet by century’s end.
John Wilmoth, the director of the population division in the United Nations Department of Economic and Social Affairs, which produces the projections every two years, said earlier findings had implicitly pointed to an end in population growth sometime around the end of the century.
The projection that growth will stall in 2100 is only an approximation, Mr. Wilmoth said in a telephone interview, but “the important point, in all likelihood, is that it will eventually stop growing.”
The 2019 projection cited declining fertility as an underlying trend. It also said people 65 or older were the fastest-growing segments of the global population.
The global fertility rate, which fell from 3.2 births per woman in 1990 to 2.5 in 2019, is expected to fall to 2.2 in 2050, the 2019 projection said.
A fertility rate of 2.1 births per woman is required to ensure replacement of generations and avert a long-term population decline in any particular country or region, absent immigration.
However, fertility rates remain high in some parts of the world — notably sub-Saharan Africa where the population could double in the next 30 years.
Mr. Wilmoth said the sub-Saharan Africa finding represents a particular challenge for achieving what the United Nations calls the Sustainable Development Goals, a list of objectives that include the elimination of poverty and hunger by 2030.
“This reinforces that the most rapid population growth is happening in areas where it is difficult to accommodate that growth,” he said.
The 2019 projection nevertheless reaffirmed that falling fertility rates globally, combined with increased life expectancy, are causing the world’s population to age. By 2050, the projection said, one in six people will be older than 65, up from one in 11 in 2019. Last year, it said, for the first time, people aged 65 or older outnumbered children younger than five years globally.
The number of people aged 80 or older, the projection said, is expected to triple from 143 million presently to 426 million by 2050.
The aging trend has troubling implications for countries with growing populations of retirees. A measurement called the potential support ratio, which compares populations of working-age people to those 65 or older, is falling around the world, the 2019 projection said.
In Japan, where the aging population is a well-known problem, the ratio is 1.8, the lowest. By 2050, the 2019 projection said, 48 countries — mostly in Europe, North America and Eastern and Southeast Asia — are expected to have ratios below two.
These low ratios, the projection said, underscore the “fiscal pressures that many countries will face in the coming decades as they seek to build and maintain public systems of health care, pensions and social protection for older persons.”
Nine countries will account for more than half the expected population growth between now and 2050, the projection said. They are: India, Nigeria, Pakistan, the Democratic Republic of Congo, Ethiopia, Tanzania, Indonesia, Egypt and the United States.
From 2010 to the present, 27 countries or areas had population reductions of at least 1 percent, because of falling fertility rates and in some cases high rates of emigration. Between now and 2050, the projection said, that number is expected to double to 55 or more, including 26 countries or areas that could see population declines of at least 10 percent.
In China, the projection said, the population is expected to fall by 32.4 million, or 2.2 percent, between now and 2050, which partly explains why India is expected to surpass China as the most populous country sometime around 2027.
The United Nations population projections, provide important benchmarks of global demographic patterns. The projections are used to help calculate a range of other important indicators, including health data, around the world.