India will surpass China to become the most populous nation in the world by 2022, six years sooner than previously forecast, and the country is projected to retain the top spot till 2100, the UN has said.
The 'World Population Prospects: The 2015 Revision' launched in United Nations on Wednesday projected that within seven years, the population of India is expected to surpass that of China.
Currently, the population of China is approximately 1.38 billion compared with 1.31 billion in India.
Around and after 2022, India's population is projected to continue growing for several decades to 1.5 billion in 2030 and 1.7 billion in 2050, while the population of China is expected to remain fairly constant until the 2030s, after which it is expected to slightly decrease.
India will remain the most populous the country in the world till 2100, according to the report.
According to the forecast issued in 2013, India was expected to surpass China's population by 2028 but the latest report predicts that India will overtake its Asian rival six years early by 2022.
The report said India will remain the most populous country in the world in 2050 with a population of 1.7 billion.
It also projected that India will continue to have the largest population size in the year 2100 even though its population will decline slightly from 1.7 billion in 2050 to 1.66 billion by the end of the 21st century.
The current world population of 7.3 billion is expected to reach 8.5 billion by 2030, 9.7 billion in 2050 and 11.2 billion in 2100.
The report said during 2015-2050, half of the world’s population growth is expected to be concentrated in nine countries -- India, Nigeria, Pakistan, Congo, Ethiopia, Tanzania, US, Indonesia and Uganda -- listed according to the size of their contribution to the total growth.
India is expected to remain a relatively young country in the decades going forward.
Its median age in 2015 is 26.6 years and this would grow to 31.2 years in 2030, 37.3 years in 2050 and 47 years in 2100.
In comparison, China's median age will be 43.2 years in 2030, 49.6 years in 2050 and 51.1 years by the end of the century.
The US will have a median age of 40 years in 2030, 41.7 years in 2050 and 44.7 years in 2100.
India's life expectancy at birth will also improve over the next decades, growing from 71.7 years in 2025-2030 to 75.9 years in 2045-2050 and 84.6 years in 2095-2100.
Globally, the number of persons aged 60 or above is expected to more than double by 2050 and more than triple by 2100.
In Europe, 34 per cent of the population is projected to be over 60 years old by 2050.
According to the results of the 2015 Revision, the world population reached 7.3 billion as of mid-2015, implying that the world has added approximately one billion people in the span of the last 12 years.
China (1.4 billion) and India (1.3 billion) remain the two largest countries of the world, representing 19 and 18 per cent of the world’s population, respectively.
It said 60 per cent of the global population lives in Asia (4.4 billion), 16 per cent in Africa (1.2 billion), 10 per cent in Europe (738 million), 9 per cent in Latin America and the Caribbean (634 million), and the remaining 5 per cent in Northern America (358 million) and Oceania (39 million).
Nigeria's population, currently the seventh largest in the world, is also growing the most rapidly.
Consequently, the population of Nigeria is projected to surpass that of the United States by about 2050, at which point it would become the third largest country in the world.
The US is projected to have a population of 389 million in 2050 which would grow to 450 million by 2100.
"Understanding the demographic changes that are likely to unfold over the coming years, as well as the challenges and opportunities that they present for achieving sustainable development, is key to the design and implementation of the new development agenda," UN Under-Secretary-General for Economic and Social Affairs Wu Hongbo said.
Large and persistent economic and demographic asymmetries between countries are likely to remain powerful generators of international migration within the foreseeable future.
Between 2015 and 2050, the top net receivers of international migrants (more than 100,000 annually) are projected to be the US, Canada, UK, Australia, Germany, Russia and Italy.
The countries projected to have net emigration of more than 100,000 annually include India, Bangladesh, China, Pakistan and Mexico.
Director of the Population Division in the UN's Department of Economic and Social Affairs John Wilmoth said concentration of population growth in the poorest countries presents its own set of challenges, making it more difficult to eradicate poverty and inequality, to combat hunger and malnutrition, and to expand educational enrolment and health systems, all of which are crucial to the success of the new sustainable development agenda.
The 2015 Revision of World Population Prospects is the 24th round of official UN population estimates and projections that have been prepared by the Population Division of the United Nations Department of Economic and Social Affairs.