World's most populous country no longer has enough babies to sustain itself

India, the most populous nation on Earth that spent half a century fighting what it called a population explosion, is now having too few children to sustain its population over the long term.

In 1950, the average Indian woman had about six children and the country held 360 million people. India overtook China in 2023 to become the world's most populous nation, according to UN data, and today is home to roughly 1.45 billion, about one-sixth of humanity.

Yet its total fertility rate, the average number of children a woman has in her lifetime, has slipped to 1.9, below the 2.1 needed to hold a population steady without migration, the UN Population Fund confirmed in its 2025 State of World Population report, titled "The Real Fertility Crisis."

In the crowded Delhi neighborhood where Parul Gayen grew up in the 1970s, big families were ordinary: her mother was one of six children, her grandfather one of 11.

Now 58, Gayen has watched her three grown children stop at a single child between them, and she worries her only grandchild will grow up alone, The Economist reported. The reversal has even reached the classroom: recently reprinted Indian textbooks no longer warn of too many children, but of too few.

In several Indian states, fertility now rivals wealthy Europe. The Economist places Tamil Nadu and West Bengal near 1.3, comparable to Finland, and Maharashtra, home to Mumbai, around 1.4, on par with Norway.

India's official Sample Registration System shows the southern states leading the decline, with Tamil Nadu posting among the country's lowest birth rates, though the BBC, citing demographers, has put the state's rate slightly higher, at around 1.4.

The effect is already hollowing out schools. In Tamil Nadu, 1,204 schools recorded no new admissions in the 2024-25 year, and 208 government schools were temporarily suspended, according to the state's Department of Elementary Education, which stressed they could reopen if enrollment recovers.

A crowd in India. Photo by Unsplash

The same story is now unfolding closer to home. Vietnam's fertility rate fell to 1.91 in 2024, its lowest ever and a third straight year below replacement, according to the General Statistics Office's mid-term population and housing survey, down from 2.01 in 2022 and 1.96 in 2023.

In Ho Chi Minh City, the rate has dropped to 1.39, the country's lowest, roughly matching Maharashtra's. The Vietnam Population Authority, under the Ministry of Health, has warned that the national population could begin shrinking after 2054.

In a near-mirror of India's textbook reversal, Vietnam scrapped its decades-old two-child limit in 2025, hoping to nudge birth rates back up.

Demographers trace the decline in both countries to the same forces. The largest, they say, is the education of girls, which since the 1990s has handed women more autonomy and a stronger voice at home, a factor the Lancet researchers identified as one of the strongest drivers of falling fertility worldwide.

Cost compounds it. As public schooling has deteriorated in India, parents have poured into private education, with the share of children in fee-paying schools climbing from 31.7% in 2015 to 38.8% in 2025, by the Economist's figures, a shift broadly mirrored in figures from India's national school census.

The contrast is with regions that still lack formal schooling, such as Niger and Chad, which the Lancet study expects to remain among the few countries above replacement through 2100.

India and Vietnam are not outliers but front-runners. A landmark 2024 study in The Lancet by the Global Burden of Disease collaborators, led by the University of Washington's Institute for Health Metrics and Evaluation, projected that by 2050, 155 of 204 countries and territories, about 76%, will sit below replacement, leaving too few workers to be backfilled by immigration alone.

Middle-income countries including Brazil, Iran and Thailand are on the same road. Demographic models see India's population peaking near 1.6 billion within two decades before a long decline, though the UN Population Fund projects a higher peak, nearer 1.7 billion over the next 40 years. Asia's total is expected to peak in the 2040s and the world's in the 2050s.

For India the squeeze is especially harsh, because it is growing old before it has grown rich, aging at a far lower income per head than earlier developed nations reached at the same stage.

Demographers say pleading with people to have more children rarely works once the trend takes hold.

The more realistic response, they say, is to help people age productively. Wealthy countries are raising retirement ages by five to seven years and reframing older citizens as a "silver generation."