Global fertility may have fallen below replacement level for the first time – study

The findings are presented in Terra Incognita: The Economics of a Shrinking World, a paper by Jesús Fernández-Villaverde of the University of Pennsylvania and Patrick Norrick of Northwestern University.

Replacement fertility is the average number of children per woman required to keep a population stable over the long term, excluding migration. Although 2.1 is commonly used as the benchmark, the study estimates the current global replacement rate at approximately 2.20 because mortality and sex ratios vary across countries.

The UN World Population Prospects 2024 places the global total fertility rate at 2.23 in 2026, based on an estimated 132.5 million births. The researchers argue that this estimate has not fully captured recent declines recorded in countries including Egypt, Mexico and the Philippines.

After adjusting for the latest birth registration data, they calculate that the global fertility rate could be no higher than 2.19 in 2026 - marginally below replacement level.

The authors acknowledge that the difference is small and subject to measurement error. They say the precise year of the crossover is less important than the direction of travel, as the available evidence consistently points toward fewer births.

Population could peak in the 2050s

Falling below replacement level does not mean the global population will begin declining immediately. Population momentum means that large generations born several decades ago are now having children, while older generations are living longer.

Nevertheless, if current trends continue, the researchers expect the world population to peak at around nine billion in approximately 2056 before beginning to decline.

This is substantially earlier than the UN’s medium projection, which anticipates a peak of 10.29 billion people in 2084. However, the researchers’ estimate is close to the UN’s low-variant scenario, which places the peak at 8.95 billion in 2053.

The authors argue that UN projections have repeatedly been revised downward. The projected population for 2100 fell from 11.21 billion in the 2015 edition of World Population Prospects to 10.18 billion in the 2024 revision.

Decline spreading across developing economies

The study analysed fertility data from 236 countries and territories between 1950 and 2023. It found negative long-term fertility trends in 219 of them, with the average country losing approximately 0.062 births per woman annually.

The common global fertility component peaked in 1978 and has declined since then. More recently, however, country-specific trends have become the main force pushing birth rates lower, with no clear indication that the decline is leveling off.

One of the most surprising developments is the speed of the decrease in lower- and middle-income economies. In 2025, the total fertility rate stood at 0.87 in Thailand, 1.01 in Colombia, 1.35 in Iran and 1.51 in Mexico. Tunisia recorded a rate of 1.45 in 2024.

According to the researchers, this challenges the traditional assumption that extremely low fertility is primarily a feature of wealthy countries.

They examine several possible explanations, including housing costs, economic uncertainty, government policy, changing social norms and the spread of smartphones. None, however, appears sufficient to explain the scale and global reach of the decline on its own.

The authors therefore offer a broader, though explicitly speculative, explanation: modern societies make larger families increasingly expensive while reducing the economic and social costs of remaining childless.

Lengthy education, demanding career schedules, high expectations for investment in each child, weaker extended-family support networks and an unequal division of childcare responsibilities can all discourage people from having additional children.

Pronatalist policies, including parental leave, housing support and cash benefits, can increase births, the paper notes, but their measured effects have generally been modest. There is also no automatic economic mechanism that would push fertility back toward replacement level.

Slower growth and pressure on pensions

A shrinking working-age population would mechanically reduce economic growth even if productivity continued increasing. It could also mean fewer entrepreneurs, researchers and highly skilled workers, while placing greater pressure on pension systems, healthcare and public debt.

The researchers point to Japan, whose GDP grew by an average of 0.79% annually between 1991 and 2023, compared with 2.60% in the United States. When measured per working-age adult, however, Japan grew by 1.33%, compared with 1.73% in the US, suggesting that much of the difference in overall growth was demographic.

Lower fertility may also bring benefits. Smaller generations can ease pressure on housing, infrastructure, natural resources and emissions. Developing economies may also have an opportunity to invest more in the education and health of fewer children before population ageing intensifies.

Kazakhstan remains above replacement, but births are declining

Kazakhstan remains among the few countries in Eastern Europe and Central Asia with fertility above the replacement level, alongside Kyrgyzstan and Uzbekistan, according to a recent UN Population Fund regional report.

However, the country is also recording fewer births. Kazakhstan registered 149,800 births in January-June 2026, compared with 161,200 during the same period of 2025 - a decline of approximately 7.1%.

Deaths remained almost unchanged at 64,700, while natural population growth fell from 96,700 to 85,100, according to Kazakhstan’s Bureau of National Statistics.

The figures indicate that Kazakhstan continues to experience natural population growth, but is not entirely insulated from the broader global decline in births.

The study concludes that fertility could recover slightly as some delayed births eventually take place. A sustained return to replacement level, however, would likely require substantial changes in how modern societies organise work, housing, education and family life.

Earlier, Qazinform reported that Kazakhstan’s population had increased to a total of 20,590,589 people as of July 1, 2026, according to the country’s National Statistics Bureau.