World faces historic population decline – study

Global fertility may have fallen below replacement level, threatening workforces, aging societies, and mounting economic pressure within roughly one generation Global fertility may have fallen below replacement level for the first time in human history, putting the world population on course for decline within roughly one generation, a new study has warned.

The paper, Terra Incognita: The Economics of a Shrinking World , published earlier this month by economics professor Jesus Fernandez-Villaverde of the University of Pennsylvania and Northwestern University researcher Patrick Norrick, warns that prolonged low fertility could shrink workforces, rapidly age societies, and strain economies and welfare systems.

The researchers estimate that humanity is likely already below replacement fertility – the average number of children per woman needed for each generation to replace itself.

The global threshold is around 2.2, while the study puts the current rate at no higher than 2.19, suggesting the world may have only just crossed it.

Read more Ukraine at 35: How a country’s population halved in three decades “As of 2026, humanity is likely to be below replacement level: we are having fewer births than we need to keep population constant in the long run… this has never happened before in our history as a species, not even during wars or pandemics,” the authors stated.

The analysis covers 236 countries and territories from 1950 to 2023, with fertility declining in 219.

On average, countries have lost around 0.062 births per woman annually, and there is little evidence the trend is leveling off, authors note.

The global population is not shrinking yet because large generations born in previous decades are still having children, but the researchers estimate this effect could sustain growth for only another three decades, with population peaking at around 9 billion in 2056 before declining.

Read more China’s demographic implosion has begun and will unfold rapidly The authors note the trend has spread well beyond rich countries, with fertility rates in 2025 estimated at just 0.87 in Thailand, 1.01 in Colombia, 1.35 in Iran and 1.52 in Brazil.

They say there is no automatic mechanism driving fertility back toward replacement level because there is no single explanation for falling birth rates: while housing and childcare costs, economic insecurity, contraception, and changing social norms may all contribute, none fully explains the global trend.

The economic consequences of the looming population decline could be far-reaching, the study warns.

Smaller generations mean fewer workers supporting growing elderly populations, straining pensions, healthcare, and public finances while slowing growth.