These estimates would mark the first time in 300 years that a country other than China holds the world's top demographic position. This was expected to occur in 2027.
In China, government policies limiting families to one child contributed greatly to reducing the country's population growth rate to 1.1 percent in the decade 1973-1983.
Despite the current freedom of families in the Asian giant to choose the number of children they wish to have, China's growth rate has not recovered.
For its part, India has been growing at a rate of 2 percent since the second half of the 20th century. However, the country's birth rate this year stands at an average of 2 births per woman, down considerably from 5.7 in 1950.
This means that the fact that India has become the most populous country in the world is because China's birth rate is declining at an even faster rate, not because of an accelerated increase in India's birth rate.
The South Asian country is also expected to contribute more than one-sixth of the projected increase in the world's working-age population by 2050. India has recently moved into fifth place among the world's largest economies, displacing Great Britain.