(CNN)The world's population is likely to peak at 9.7 billion in 2064, and then decline to about 8.8 billion by the end of the century, as women get better access to education and contraception, a new study has found.
World's population likely to shrink after 50 years
By 2100, 183 of 195 countries will not have fertility rates required to maintain the current population, with a projected 2.1 births per woman, researchers from the Institute for Health Metrics and Evaluation at the University of Washington's School of Medicine said.
Some 23 countries -- including Japan, Thailand, Italy, and Spain -- will see populations shrink by more than 50%, researchers said.
However, the population of sub-Saharan Africa could triple, allowing for just under half of the world's population to be African by the end of the century.
The modeling study, published Tuesday in The Lancet, also forecasts dramatic declines in working-age populations in countries including India and China, which will hurt economic growth and could have negative implications for labor forces and social support systems, researchers said.
But as fertility declines, researchers note that immigration could offset population shrinkage, particularly in countries with low fertility, such as the US, Australia and Canada.
"The world, since the 1960s, has been really focused on the so-called population explosion," Dr Christopher Murray, who led the research, told CNN. "Suddenly, we're now seeing this sort of turning point where it is very clear that we are rapidly transitioning from the issue of too many people to too few."
Using data from Global Burden of Disease Study 2017, researchers predicted that the fastest-shrinking populations will be in Asia and eastern and central Europe.
The report authors project that the population of Japan will shrink from around 128 million people in 2017 to 60 million in 2100, Thailand will see a shrink from 71 to 35 million, Spain 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.
A further 34 countries -- including China -- are also predicted to see their population decline by up to 50%.