Earth To Have Nearly 11 Bn People By 2100: UN

“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 percent chance that the population in Africa at the end of the century will be between 3.5 billion and 5.1 billion people,” Raftery pointed out.

Populations in North America, Europe, and Latin America and the Caribbean are projected to stay below one billion each.

The paper explains the most recent UN population data released in July.

World population projections are based mostly on two things: future life expectancy and fertility rates. Earlier techniques relied largely on expert opinion for how those trends were expected to change.

The newer forecast uses modern statistics known as Bayesian statistics to combine government data and expert forecasts for such things as mortality rates, fertility rates and international migration.

Earlier reports represented uncertainty by using scenarios in which women would have 0.5 children more or less than the experts' forecast. That method, Raftery said, generates too great a range.

The new method used statistical models to narrow the range, finding an 80 percent probability that the population in 2100 will be between 9.6 billion and 12.3 billion, researchers maintained.

The research, supported by the U.S. National Institute of Child Health and Human Development and Science Foundation Ireland, appeared in the journal Science.

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