Global birth rate must rise to 2.7 to avoid extinction, researchers warn

A new study suggests humanity may need a higher birth rate than previously thought to ensure its long-term survival. According to researchers, women would need to have at least 2.7 children each—far above the widely accepted global replacement rate of 2.1—to prevent population decline over generations.

The findings come from a team led by Professor Takuya Okabe at Shizuoka University’s Graduate School of Integrated Science and Technology in Japan. The team published its analysis Wednesday in the journal PLOS ONE.

For decades, the replacement fertility rate has been set at 2.1 children per woman, a figure meant to offset deaths and sustain a stable population. Total fertility rate refers to the average number of children a woman is expected to have during her reproductive years.

But as fertility rates fall worldwide, concerns about shrinking populations are rising. The global rate has plunged from more than five in the 1960s to 2.25 in 2023. Today, about two-thirds of the world’s people live in regions where fertility is below the replacement threshold. South Korea, for instance, recorded a rate of just 0.72 last year—the lowest in the world—posing serious risks to its future sustainability.

Using mathematical models, Okabe’s team examined how random factors and demographic shifts affect long-term population stability. Their analysis shows that to reliably maintain population levels across generations, the minimum fertility rate needs to be 2.7 children per woman—substantially higher than current targets.


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