What will the world's population look like by the end of the century? Older, less fertile and less numerous than expected, according to the latest estimates from the United Nations (UN) Department of Economic and Social Affairs, published on Thursday July 11. Demographers have revised their projections slightly downwards. They now estimate that humanity will continue to grow for the next fifty years, peaking at 10.3 billion in the mid-2080s, before declining to 10.2 billion in 2100. Nearly 200 million fewer than projected in 2022, and 700 million fewer than estimated 10 years ago.
This reassessment, which is good news for the planet according to some, and a crime of lèse-humanité for others, is largely due to the decline in fertility in some of the world's largest countries, led by China. "The demographic landscape has changed considerably in recent years," points out Li Junhua, Under-Secretary-General for Economic and Social Affairs at the United Nations. In some countries, birth rates are even lower than expected, and we're also seeing slightly faster declines in some high-fertility regions."
At the heart of this puzzle is the total fertility rate (TFR). It is calculated on the basis of the number of births and the number of women of childbearing age at a given point in time, and is highly dependent on recent changes in behavior and offers only a hypothetical vision of the number of children each woman will have in her lifetime.
"Fertility has a duplicative effect across generations," insists Patrick Gerland, who coordinates the UN's population projections. "For example, if fertility remained constant in all countries until the end of the century, humanity would reach 18 billion individuals. Variations in mortality assumptions do not lead to such large differences." UN demographers estimate that the most likely scenarios today place humanity somewhere between 9 and 11.4 billion people by 2100.
In China, the TFR dropped from 1.2 children per woman in 2022 to 1 in 2024, a historically low level. Even though it was outpaced by India in 2023, China remains the world's second most populous country, with 1.4 billion inhabitants. Such a sharp decline in such a populous country is bound to have major global implications. "China is facing the legacy of the changes that have taken place over the last thirty years in the one-child policy. Most people of child-bearing age today grew up as an only child themselves, which necessarily has an impact in terms of social and family norms," analyzes Patrick Gerland. An unprecedented challenge, especially in a country of this size.
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