Passengers travel on an overcrowded train at Loni town, in the northern Indian state of Uttar Pradesh, on July 8, 2014. (Anindito Mukherjee/Reuters)

India is poised to become the world's most populous country six years earlier than expected, according to revised population projections released Wednesday by the United Nations.

A new report by the population division of the United Nations Department of Economic and Social Affairs says China and India have about 1.38 billion and 1.31 billion people, respectively. After 2022, when both are expected to have about 1.4 billion, India's population will continue rising and China's will "remain fairly constant" until the 2030s, at which point it will begin to "slightly decrease."

That will occur six years earlier than the organization projected two years ago, when it acknowledged 2028 as the year India would likely pass China. India, which accounts for 18 percent of the world's population, is projected to reach 1.5 billion people in 2030 and 1.7 billion in 2050.

The global population, currently at 7.3 billion, is predicted to hit 9.7 billion by 2050. Much of that growth is projected to occur in high-fertility nations, mostly throughout Africa, or ones with large populations.

Between 2015 and 2050, the report notes, nine nations are expected to account for more than half of the world's projected growth: India, Nigeria, Pakistan, the Democratic Republic of Congo, Ethiopia, Tanzania, the United States, Indonesia and Uganda.

Also highlighted in the report is a rise in global life expectancy at birth, from 67 years between 2000-2005 to 70 years in 2010-2015. That trend is expected to continue, reaching 77 years in 2045-2050 and then 83 years in 2095-2100.

By the end of the century, Africa's life expectancy of about 60 years is predicted to rise by nearly 19 years. That increase, the report says, is dependent on further reducing the spread of HIV and other infectious or non-communicable diseases.

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