The world's population will hit 7 billion early in 2012 and cross 9 billion in 2050, with the majority of the increase taking place in developing countries, revised United Nations estimates show.

India, United States, China, Bangladesh and Pakistan are among nine countries which are projected to account for half of the world's population increase from 2010 to 2050. The others are Nigeria, Ethiopia, the Democratic Republic of Congo (DRC) and Tanzania.

"There have been no big changes for the recent estimates and we have not changed the assumptions for the future," Hania Zlotnik, Director of the Population Division at the Department of Economic and Social Affairs, told reporters yesterday.

"We're still projecting that by 2050 the population of the world will be around 9.1 billion," she said, as she presented the 2008 Revision of the World Population Prospects.

Zlotnik noted that current projections are based on the assumption that fertility is going to decline from the current global level of 2.5 children per woman to 2.1 children per woman from now until 2050.

The population of the 49 least developed countries (LDCs) is still the fastest growing in the world, at 2.3 per cent per year, the Population Division said.