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The study, led by a team of researchers at University of Washington’s Institute for Health Metrics and Evaluation (IHME), analysed population trends in 195 countries. It used data from the Global Burden of Disease Study 2017 to model future population in various scenarios as a function of fertility, migration, and mortality rates.

The broad takeaways

IHME director Dr Christopher Murray, who led the research, said the forecasts highlight huge challenges to the economic growth of a shrinking workforce, the high burden on health and social support systems of an ageing population.

The paper suggests that continued trends in female educational attainment and access to contraception will hasten declines in fertility and slow population growth.

For a generation to exactly replace itself, the replacement-level total fertility rate (TFR) is taken to be 2.1, representing the average number of children a woman would need to have. In the study, the global TFR is predicted to steadily decline from 2.37 in 2017 to 1.66 in 2100. The TFR is projected to fall below 2.1 in 183 countries. In 23 countries including Japan, Thailand, Italy and Spain, it is projected to shrink by more than 50%.

Source: Vollset, Goren et al/The Lancet

Key numbers: India

“Trends in India’s total population and in the population of working age adults will follow similar trends,” Stein Emil Vollset, one of the lead authors, told The Indian Express by email. “The total population will increase and peak just before mid-century, followed by significant declines. Similarly, the working-age population will also increase in the first half of the century, and then decline in the second half. These declines are driven by fertility rates, which we forecast will continue declining over the next few decades,” Vollset said.

?? India’s TFR was already below 2.1 in 2019. The TFR is projected to have a continue a steep decline until about 2040, reaching 1.29 in 2100.

?? The number of working-age adults (20–64 years) in India is projected to fall from around 748 million in 2017 to around 578 million in 2100. However, this will be the largest working-age population in the world by 2100. In the mid-2020s, India is expected to surpass China’s workforce population (950 million in 2017, and 357 million in 2100).

???From 2017 to 2100, India is projected to rise up the list of countries with the largest GDP, from 7th to 3rd.

???India is projected to have the second largest net immigration in 2100, with an estimated half a million more people immigrating to India in 2100 than emigrating out.

???Among the 10 countries with the largest populations in 2017 or 2100, India is projected to have one of the lowest life expectancies (79.3 years in 2100, up from 69.1 in 2017).

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The road ahead

In a commentary on the research, Ibrahim Abubakar of University College London’s Institute for Global Health, stresses the need for countries to address the potential catastrophic impact of a shrinking working-age population, and suggests measures such as incentives to increase TFR, and using artificial intelligence as a path towards self-sufficiency.

“Wealthy countries such as the UK and the USA could counteract the impact of these changes through net migration of working-age adults from the countries with growing populations. Unfortunately, the election of nationalist rulers, associated decline in multilateralism, and increasing hostility to migration makes this option unlikely in the short term,” Abubakar wrote.

Professor Usha Ram from the Department of Public Health and Mortality Studies at the International Institute for Population Sciences, Mumbai, who was not involved in the study, too discussed the impact of migration when contacted.

“Migration, rather liberal migration policies… could be a solution but not permanent. However, what is more important is to look to invest in technological advancements that can compensate for the human shortages. For example, Japan has managed the needs of its greying population with virtually no emphasis on migration,” she said.

She said the effect of fertility decline on women’s reproductive health rights has to be accompanied by greater economic independence. “This would allow women to negotiate with the system on their own terms and for better support services as well.”