Scientists have predicted that the India's population may peak to about 1.6 billion in 2048, and decline by 32 per cent to around 1.09 billion in 2100, when it is also expected to be the world's most populous country.
The analysis, published in the journal The Lancet, used data from the Global Burden of Disease Study 2017, and applied novel models to project future global, regional, and national population for 183 countries, including India, US, China, and Japan, and their mortality, fertility, and migration rates.
According to the researchers, including those from the University of Washington in the US, there may be dramatic declines in working age-populations in countries such as India and China, which they said may hamper economic growth and lead to shifts in global powers.
They said the world could be multipolar at the end of this century, with India, Nigeria, China, and the US the dominant powers.
"This will truly be a new world, one we should be preparing for today," the scientists noted.
According to the study, the numbers of working-age adults in India is projected to fall from 762 million in 2017 to around 578 million in 2100, compared to that of China where numbers of workers are estimated to decline from 950 million in 2017 to 357 million in 2100.
It said India may be one of the few - if only major power in Asia to protect its working-age population over the century.
"It is expected to surpass China's workforce population in the mid-2020s, rising up the GDP rankings from 7th to 3rd," the scientists noted in a statement to the press.
Commenting on the research, Christopher Murray from the University of Washington, who led the research, said continued global population growth through the century is no longer the most likely trajectory for the world's population.
"This study provides governments of all countries an opportunity to start rethinking their policies on migration, workforces and economic development to address the challenges presented by demographic change," Murray said
Citing the study's limitations, the scientists said while they used the best available data, predictions are constrained by the quantity and quality of past data.
They also added that past trends are not always predictive of what will happen in the future, and that some factors not included in the model could change the pace of fertility, mortality, or migration.
According to the scientists the COVID-19 pandemic has affected local and national health systems throughout the world, and caused over half a million deaths.
However, they said the excess deaths due to the pandemic are unlikely to significantly alter longer term forecasting trends of global population.