The bulk of the expected increase in global population is likely to come from 58 "high-fertility countries" in Africa, Asia, Oceania, and Latin America, said the report "2010 Revision of World Population Prospects" which was prepared by the UN Department of Economic and Social Affairs (DESA) .

Hania Zlotnik, director of the DESA's Population Division, told reporters here that fertility is "the main driver of population rates in the world".

"The world hasn't collapsed by adding so many people, but what is important is that most of these people are being added in the poorest countries of the world," he said.

Based on the medium projection, the number of people in the world -- currently close to 7 billion -- should pass 8 billion in 2023, 9 billion by 2041 and then 10 billion at some point after 2081, according to the report.

Between 2011 and 2100, the population of high-fertility countries is expected to more than triple in size, going from 1.2 billion to 4.2 billion, the report noted. During the same period, the report predicted, the population of low-fertility countries will decline by around 20 percent -- from 2.9 billion to 2.4 billion.

Xinhua