India, already bursting at the seams with over a billion people, will overtake China earlier than expected to become the world's most populous country.
The United Nation's population-studies body that monitors global trends has revised its past estimates to now conclude that India would overtake China earlier than anticipated and touch 1.5 billion in 2030.
China's population growth will remain fairly constant in the same period as a result of its one-child policy which has been slightly relaxed recently.
India will face severe developmental challenges as a result. Unlike China, which maintained double digit growth for over a decade, India has struggled to reach even 9 percent growth in its GDP. John Wilmoth, head of the U.N. population division, said the concentration of growth in the poorest countries would make it harder to eradicate poverty, combat hunger and expand schooling and health systems.
The situation is likely to ease only by 2050 when the population growth might slow after touching 1.7 billion in 2050 and eventually see a decline around 2100. Higher birthrate and declining death rates will accelerate the number of inhabitants, and make it more difficult to raise India's already abysmal position in the world human development index.
Fast-growing Nigeria is on course to outstrip the United States by about 2050 to become the country with the third largest population, the report added.
The current global population of 7.3 billion is forecast to reach 9.7 billion in 2050 and 11.2 billion in 2100, slightly above the last set of U.N. projections. Most growth will happen in developing regions, particularly Africa, according to the report World Population Prospects.
The demographic forecasts are crucial for designing and implementing the new global development goals being launched later this year to replace the Millennium Development Goals.
Experts predict Africa will account for more than half the world's population growth in the next 35 years. Currently, 60 per cent of the global population lives in Asia, 16 per cent in Africa, 10 per cent in Europe, 9 per cent in Latin America and the Caribbean, and the remaining 5 per cent in North America and Oceania.
Ten African countries - Angola, Burundi, Democratic Republic of Congo, Malawi, Mali, Niger, Somalia, Uganda, Tanzania and Zambia - are projected to increase their populations five-fold or more by 2100.
Future population growth is highly dependent on the path of future fertility, as relatively small changes in fertility can, projected over decades, generate large differences in total population, the report said.
In recent years, fertility has declined in almost all parts of the world, while life expectancy has increased significantly in the poorest countries, rising from 56 to 62 since the beginning of the century. Declining fertility and rising life expectancy mean the world is getting greyer, and most regions will have an ageing population, starting with Europe where one third of the population is projected to be over 60 by 2050, the report said.
Globally, the number of people aged 80 or over - currently 125 million - is projected to more than triple by 2050 and to increase more than seven times by 2100.
But populations in many regions are still young. In Africa, children under 15 account for two fifths of the population. "The large number of young people (in Africa) who will reach adulthood in the coming years and have children of their own, ensures that the region will play a central role in shaping the size and distribution of the world's population over the coming decades," the report said.
India's demographic will shift towards a higher median, the UN said. The median age of Indians, currently 26.6 years, will grow to 31.2 years in 2030, 37.3 years in 2050 and 47 years in 2100. In the same time, China's median age will reach 51.1 years. The United States will actually get younger than India and China, with projected median age of 40 years in 2030, 41.7 years in 2050 and 44.7 years in 2100.