The study, led by UN demographer Patrick Gerland and Adrian Raftery from the University of Washington puts the likelihood of the population being between 9.6 billion and 12.3 billion by the end of the century at 80%.

According to Raftery, contrary to previous predictions that the world population growth would begin to slow or decline, the new prediction puts the likelihood of this happening at 30%.

"Previous forecasts did indeed forecast a leveling off of the world population around 2050, and in some cases a decline," Raftery noted.

The new predictions are based on the fact that population growth in Sub-Saharan Africa has not been declining as fast as was previously predicted. The region is expected to have a population of between 3.5 and 5.1 billion by the end of the century, compared to around 1 billion today.