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'a 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.