The population of almost every country will be shrinking by the end of the century, a major study said, warning that baby booms in developing nations and busts in rich ones will drive massive social change.
The fertility rate in half of all nations is already too low tomaintain their population size, an international team of hundreds of researchers reported in The Lancet.
Using a huge amount of global data on births, deaths and what drivesfertility, the researchers tried to forecast the future for the world’s population.
By 2050, the population of three quarters of all countries will be shrinking, according to the study by the US-based Institute For Health Metrics and Evaluation (IHME).
At the end of the century, that will be true for 97 percent—or 198 out of 204 countries and territories, the researchers projected.
Only Samoa, Somalia, Tonga, Niger, Chad and Tajikistan are expected to have fertility rates exceeding the replacement level of 2.1 births per female in 2100, the study estimated.
During this century, fertility rates will continue to increase in developing countries, particularly those in sub-Saharan Africa, even as they tumble in wealthier, ageing nations.
“The world will be simultaneously tackling a ‘baby boom’ in some countries and a ‘baby bust’ in others,” senior study author Stein Emil Vollset of the IHME said in a statement.
“We are facing staggering social change through the 21st century,” he said in a statement.
IHME researcher Natalia Bhattacharjee said the “implications are immense.”
However, World Health Organization experts urged caution for the projections. They pointed out several limitations of the models, particularly a lack of data from many developing nations.
Communication about the figures “should not be sensationalized, but nuanced, balancing between gloom and optimism,” the WHO experts wrote in The Lancet.