Projections of human popuations to 2100, per continent. New data and methods show that population cold be as high as 12 billion by the year 2100. Graphic: Gerland, et al., 2014
Projections of human popuations to 2100, per continent. New data and methods show that population cold be as high as 12 billion by the year 2100. Graphic: Gerland, et al., 2014

By Felicity Nelson     
20 September 2014

(Science Alert) – For over a decade, experts worldwide have assumed that population growth would level off by 2050, reaching approximately 9 billion. Now, new projections have turned that analysis on its head. The population analysis, published in Science this week, was conducted by demographer Patrick Gerland from the United Nations and sociologist and statistician Adrian Rafferty from the University of Washington in the US. The study made use of Bayesian probabilistic methodology to show that there is an 80 per cent probability that the world’s population, now 7.2 billion, would increase to between 9.6 and 12.3 billion by 2100.

“Projections up to about 10 years ago projected world population to keep growing to about 9 billion in 2050, and then to level off or decline,” Raftery told New Scientist. “But our results suggest this levelling off is unlikely.”

Previous studies assumed that education and access to contraception would drastically slow population growth in Africa. However, the birth rate has only slightly decreased across the continent in the last 10 years. The researchers reported that Africa’s population would rise from 1 to 4 billion in the next century.

“The combination of a new method that’s not based on assumption but is based directly on data, and also the new data on Africa, have combined to make quite a big change to the overall population projections,” Raftery told Science.

The world’s population could reach 12 billion by 2100 

ABSTRACT: The United Nations recently released population projections based on data until 2012 and a Bayesian probabilistic methodology. Analysis of these data reveals that, contrary to previous literature, world population is unlikely to stop growing this century. There is an 80% probability that world population, now 7.2 billion, will increase to between 9.6 and 12.3 billion in 2100. This uncertainty is much smaller than the range from the traditional UN high and low variants. Much of the increase is expected to happen in Africa, in part due to higher fertility and a recent slowdown in the pace of fertility decline. Also, the ratio of working age people to older people is likely to decline substantially in all countries, even those that currently have young populations.

World population stabilization unlikely this century