Earth on the Brink: Global Fertility Falls Below Replacement Level, Economy Under Threat
The global fertility rate is estimated to have fallen below the replacement level for the first time in human history. This critical condition places the world population on a path of drastic decline within just one generation.
The warning was set out in a new study titled “Terra Incognita: The Economics of a Shrinking World”. The paper, published earlier this month, was written by economics professor Jesus Fernandez-Villaverde of the University of Pennsylvania and researcher Patrick Norrick of Northwestern University.
Jesus and Patrick warned that prolonged low fertility rates could shrink the labour force, rapidly age societies, and place a massive burden on economies and welfare systems.
The researchers estimate that humanity is likely already below the replacement fertility rate, namely the average number of children per woman needed for each generation to replace itself. The global threshold stands at around 2.2, while the study places the current rate at no higher than 2.19.
“Starting in 2026, humanity is likely below the replacement level: we have fewer births than we need to keep the population constant in the long run… this has never happened before in our history as a species, even during wars or pandemics,” the paper stated.
The analysis covered 236 countries and territories from 1950 to 2023, with fertility rates recorded as declining significantly in 219 countries. On average, countries have lost around 0.062 births per woman each year, and there is no evidence at all to suggest that this trend will begin to level off.
The global population has not yet shrunk because the large generations born in previous decades are still having children. However, the researchers estimate that this effect will only be able to sustain growth for another three decades, with the population peaking at around 9 billion in 2056 before eventually declining.
This alarming trend has also spread far beyond wealthy countries. Fertility rates in 2025 are estimated at just 0.87 in Thailand, 1.01 in Colombia, 1.35 in Iran, and 1.52 in Brazil. There is no automatic mechanism that can push fertility back to replacement levels because the triggers are highly varied and have no single explanation, ranging from housing and childcare costs, economic insecurity, contraceptive use, to changing social norms.
The study stressed that the economic consequences of population decline will be extremely wide-ranging. Smaller generations mean fewer workers to support a growing elderly population, placing severe strain on pension funds, healthcare, and public finances while simultaneously slowing growth.
In the United States, the researchers project that annual productivity growth of 2% combined with a 0.5% labour force contraction would cut long-term gross domestic product (GDP) growth to only around 1.5%.