Glossary term
Demographic transition
The historical process by which a society shifts from high birth rates and high death rates to low birth and low death rates. During the transition — which can take decades to centuries — death rates fall before birth rates, causing a period of rapid population growth. This four-stage model is the foundational framework of modern demography and explains why global population grew from 1 billion to 8 billion in just 200 years.
Pre-transition
High birth rates, high death rates. Slow or no growth. Dominant for most of human history before ~1800.
Early transition
Death rates fall (sanitation, medicine). Birth rates remain high. Population grows rapidly. Sub-Saharan Africa today.
Late transition
Birth rates begin to fall. Growth slows. India, South Asia, Latin America today.
Post-transition
Low birth rates, low death rates. Near-zero or negative natural growth. Europe, Japan, South Korea today.
Why the transition causes explosive growth
The central insight of the demographic transition model is the gap between falling death rates and still-high birth rates in Stage 2. Before the transition, high birth rates were needed to offset high child mortality — many children died before adulthood. When sanitation, vaccines, and food security lowered child mortality, the births kept coming for a generation before behaviour adapted.
This gap is why the world went from 1 billion people in 1800 to 2 billion in 1927, 4 billion in 1974, and 8 billion in 2022. The growth was not caused by rising birth rates but by falling death rates. You can see this pattern in the explorer — the ridgeline lanes for countries in Stage 2 show steep upward slopes that flatten as Stage 3 progresses.
The Gapminder Foundation has visualised this transition for every country, showing the same S-curve trajectory of birth rates following death rates down with a lag.
Where countries are today
Most high-income countries completed the transition in the 20th century and are now firmly in Stage 4. Japan's TFR is 1.2; Germany's is 1.5; South Korea's reached 0.72 in 2023 — the lowest ever recorded for a major country. These countries face the post-transition challenge: population ageing, shrinking labour forces, and the need for replacement migration.
India completed its transition later but effectively: from a TFR of 5.9 in 1960 to about 2.0 today — just at replacement level. India's story is analysed in detail in our article on India surpassing China. Southeast Asia (Vietnam, Thailand, Indonesia) moved through the transition rapidly from the 1970s–2000s.
Sub-Saharan Africa remains in Stage 2–3. Nigeria's TFR is above 5.1. Niger's exceeds 6.5 — the highest in the world. The UN WPP 2024 projects that Africa's total population will more than double from 1.4 billion today to about 3.8 billion by 2100, accounting for nearly all global population growth in that period. See our article on sub-Saharan Africa as the global growth engine.
A proposed Stage 5 — below-replacement equilibrium
Several demographers, including those at the Vienna Institute of Demography, have proposed a fifth stage in which fertility stabilises significantly below replacement level, causing gradual natural population decline. South Korea, with a TFR of 0.72, is the extreme case. Whether this is a permanent endpoint or a transitional phase from which fertility will recover — as it did partially in Northern Europe in the 1980s–1990s — is unresolved.
The implication of a Stage 5 world would be eventual global population decline, possibly before 2100. The 2024 Lancet study projected peak world population before 2060 under its central scenario, with decline thereafter — a significant departure from earlier UN projections. Read more in our article on global fertility approaching replacement level.
Frequently asked questions
What is the demographic transition?
The demographic transition is the historical shift a society undergoes from high birth rates and high death rates to low birth rates and low death rates. It moves through roughly four stages, with rapid population growth occurring during Stage 2 when death rates fall before birth rates adjust. The model was first formalised by demographer Frank Notestein in 1945, drawing on observations of European population history.
Why does population grow so fast during the demographic transition?
Population grows rapidly in Stage 2 and early Stage 3 because death rates fall first — driven by improvements in sanitation, medicine, and food supply — while birth rates remain high for a generation or more afterward. This gap between falling deaths and still-high births creates a period of rapid natural increase. It is why global population grew from 1 billion in 1800 to 8 billion in 2022.
Where are different countries in the demographic transition today?
Most high-income countries are in Stage 4 (low birth and death rates, near-zero or negative natural growth). Middle-income countries like India, Brazil, and Indonesia are in late Stage 3. Much of sub-Saharan Africa — particularly Nigeria, Niger, Mali, and Chad — is in Stage 2 or early Stage 3, with high fertility but rapidly falling child mortality.
Is there a Stage 5 of the demographic transition?
Some demographers propose a Stage 5 in which fertility falls significantly below replacement level (below 1.5), causing natural population decline without immigration. South Korea (TFR 0.72 in 2023), Japan (1.2), and most of Southern and Eastern Europe are candidates. Whether this is a stable endpoint or a temporary phase from which fertility will recover is one of the most contested questions in contemporary demography.