Global fertility rate edges closer to replacement level
The world average total fertility rate has fallen to roughly 2.3 children per woman — close to but still above the 2.1 replacement threshold. More than half of all countries are already below that line, yet global population keeps growing. Understanding why requires separating fertility from momentum.
The number behind the headline
In 1950 the global total fertility rate (TFR) was approximately 5.0 children per woman. By 2023 the UN World Population Prospects 2024 estimated it had fallen to about 2.3 — a halving over 70 years. That decline is the central demographic fact of the modern era, driven by urbanisation, rising female education, improved access to contraception, and shifting family norms.
Of the world's roughly 200 countries, more than half now record a TFR below 2.1 — the level demographers call replacement level. These include virtually all of Europe, most of East Asia and Latin America, and an increasing share of South and South-east Asia. The global average stays above 2.1 only because a cluster of high-fertility countries — concentrated in sub-Saharan Africa — are home to large and still-growing populations.
Why population keeps growing even as fertility falls
This is one of demography's most counterintuitive results. When a country's TFR drops below 2.1, its population does not immediately begin to shrink — it often continues growing for another 50 to 70 years. The reason is population momentum: the large cohorts born during high-fertility decades are still alive, still having children (even if fewer), and still adding births that outnumber deaths for decades to come. The Population Reference Bureau's primer on momentum explains the mechanism in detail.
This is visible in countries like Iran and Brazil, whose TFRs fell below 2.1 years ago but whose total populations are still growing. It explains why the 8 billion mark was reached in 2022 even though more countries were below replacement than above it. The metric that matters for the near-term total is not TFR but the absolute number of births and deaths — and births still outnumber deaths globally by a margin of roughly 80 million people per year.
The Lancet 2024 projection: peak before 2060
A study published in The Lancet in March 2024, using the Institute for Health Metrics and Evaluation (IHME) methodology, offered a more aggressive fertility forecast than the UN's. The IHME model projects global TFR falling to around 1.6 by 2100 — well below replacement — and puts peak world population at roughly 9.7 billion, arriving before 2060. After that, under their central estimate, population begins a slow decline.
The key divergence from the UN median variant is in sub-Saharan Africa. IHME forecasts faster fertility decline in Nigeria, Ethiopia, and neighbouring countries as female education and urban migration accelerate. The UN is more conservative about the pace of that transition. Both institutions publish their full assumptions and data openly — the UN WPP download portal and the IHME research pages both allow scenario comparisons.
Where fertility is highest — and lowest
The most striking contrast is between sub-Saharan Africa and East Asia. Niger has the world's highest TFR at approximately 6.7, while South Korea reached a record low of 0.72 in 2023 — a level with no modern precedent in any country. Seoul, the South Korean capital, recorded a TFR of just 0.55 that year. At that rate, a cohort of 1,000 women would collectively have only 550 daughters — the population would roughly halve every generation. The Korean Statistical Information Service publishes annual updates.
Japan, Italy, Spain, Greece, and Germany all record TFRs between 1.2 and 1.5. These countries are managing the consequences now: shrinking working-age populations, rising dependency ratios, and pension systems built on demographic assumptions that no longer hold. Our World in Data maintains live country TFR charts updated from the UN WPP data.
What it means for long-run projections
Small differences in the assumed trajectory of TFR produce enormous differences in long-run population totals. A global TFR that stabilises at 2.1 implies a world of 11+ billion by 2100. A TFR that falls to 1.7 implies a peak and decline to under 7 billion by century's end. This sensitivity is why the UN publishes multiple variants — low, medium, and high — rather than a single forecast. The medium variant is the standard reference, but the range reflects genuine uncertainty.
In the PopulationTheGuide explorer, projection data comes from the UN medium variant by default. You can see individual country trajectories — including the divergence between high-fertility and low-fertility countries — by loading country ridgelines on the main canvas and toggling the projection view.
Frequently asked questions
What is the current global fertility rate?
The UN WPP 2024 estimates the global TFR at approximately 2.3 as of 2023, down from 5.0 in 1950. More than half of all countries are already below the 2.1 replacement threshold.
What does below-replacement fertility mean for population growth?
Below-replacement fertility does not stop growth immediately. Population momentum — large young cohorts still moving through reproductive age — keeps numbers rising even after TFR falls below 2.1. Growth only stops when that momentum is exhausted, typically two generations later.
When will global population start declining?
Under the UN median variant, population peaks at around 10.4 billion in the 2080s. The 2024 Lancet/IHME model puts the peak lower — around 9.7 billion before 2060 — with a slow decline beginning shortly after.
Which country has the lowest fertility rate?
South Korea recorded a TFR of 0.72 in 2023, the lowest ever recorded in any country. Seoul itself reached 0.55. Several other countries in East Asia and Southern Europe also record TFRs below 1.3. At these levels, populations would roughly halve every generation without immigration.