India looks set to overtake China as the world's most populous country from 2028, according to the United Nations.

At that point, both nations will number 1.45 billion people each. Subsequently India's population will continue to grow until the middle of the century, while China's slowly declines.

The UN also estimates that the current global population of 7.2 billion will reach 9.6 billion by 2050.

That is a faster rate of growth than previously estimated.

http://www.bbc.co.uk/news/world-asia-22907307

Nigeria expected to have larger population than US by 2050

Nigeria's population is expected to surpass that of the US by 2050, according to new UN projections that predict the west African country could be the world's third most populous by the end of this century.

The UN report World population prospects: the 2012 revision, published on Thursday, predicts the world's population, now at 7.2 billion, will reach 8.1 billion in 2025. By mid-century, the world's population is expected to top 9.5 billion, reaching nearly 11 billion by 2100.

More than half of the growth predicted between now and 2050 is expected in Africa, where the number of people is set to more than double, from 1.1 billion to 2.4 billion. Africa's population will continue to rise even if there is a future drop in the average number of children each woman has, says the report, which predicts the number of people living on the continent could reach 4.2 billion (or more than 35% of total global population) by 2100.

Several other countries, including India, Indonesia, Pakistan and the Philippines, are also set for significant population increases.

http://www.guardian.co.uk/global-development/2013/jun/13/nigeria-larger-population-us-2050