A major new study finds that world population is likely to keep growing longer than anyone thought.
The number of people on Earth is likely to reach 11 billion by 2100, about 2 billion higher than some estimates.
The results of the study led by the University of Washington and the United Nations are published in the journal Science.
“The consensus over the past 20 years or so was that world population, which is currently around 7 billion, would go up to 9 billion and level off or probably decline,” says Adrian Raftery, a professor of statistics and of sociology at the University of Washington.
“We found there’s a 70% probability the world population will not stabilize this century. Population, which had sort of fallen off the world’s agenda, remains a very important issue.”
The paper explains the most recent United Nations population data released in July. This is the first UN population report to use modern statistics, known as Bayesian statistics, that combines all available information to generate better predictions.
Most of the anticipated growth is in Africa, where population is projected to quadruple from around 1 billion today to 4 billion by the end of the century.
The main reason is that birth rates in sub-Saharan Africa have not been going down as fast as had been expected.
There is an 80% chance the population in Africa at the end of the century will be between 3.5 and 5.1 billion people.
Other regions of the world are projected to see less change.
Asia, now 4.4 billion, is projected to peak at around 5 billion people in 2050 and then begin to decline.
Populations in North America, Europe, and Latin America and the Caribbean are projected to stay below 1 billion each.
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