A woman in Niger has, on average, close to seven children over her lifetime. A woman in South Korea has fewer than one. That tenfold gap between the world’s highest and lowest fertility countries is the single most important fact for understanding modern family size, a range so wide that it makes any single global average nearly meaningless without also showing the distribution behind it.
What Does “Family Size” Mean?
Three distinct measures get used, often interchangeably, when discussing family size, and distinguishing them is essential to reading fertility data correctly. Household family size refers to the number of related people living together in one home.
Total fertility rate (TFR) is a period measure: the number of children a woman would have if she experienced a given year’s age-specific birth rates throughout her reproductive life. Completed fertility, or children ever born, measures the actual lifetime number of children born to women who have finished their childbearing years, typically assessed around age 45 to 49.
TFR is the most commonly reported figure because it can be calculated every year from current birth data, but it is also the most sensitive to short-term shifts in the timing of births, which is why it can move differently than completed fertility, especially during periods of rapid delay in average childbearing age.
How Many Children Do Women Have Around the World?
The global TFR fell from about 5.3 children per woman in 1963 to 2.2 by 2023, according to World Bank data cited in recent compilations, a decline of more than half within sixty years even as the global population more than doubled over the same period, from 3.2 billion to 8.1 billion, a divergence explained by longer life expectancy and sharply falling child mortality rather than by births alone.
Global Total Fertility Rate Over Time
| Year | Global TFR (Children per Woman) |
|---|---|
| 1963 | ~5.3 |
| 1990 | ~3.3 |
| 2023-2024 | ~2.2 |
Source: World Bank data, as compiled in Statista’s “State of Global Fertility” analysis; UN World Fertility 2024.
Where Families Remain Large
Niger holds the highest total fertility rate of any country, estimated at 6.64 to 6.73 children per woman in recent data, alongside a median national age of just 14.8 to 15.1 years, meaning half the country’s population has not yet reached its teenage years. Chad, the Democratic Republic of the Congo and Somalia followed closely behind at approximately 6.1 in 2023 estimates, with the Central African Republic and Mali not far behind.
Of the 31 countries worldwide where women had 4 or more children on average in 2023, 29 were in Africa, underscoring how concentrated high fertility has become geographically, even as it remains a genuinely global phenomenon in its broader downward trend.
Niger’s own demographic profile illustrates why high fertility persists there specifically: the country’s fertility decline has stalled in recent decades, largely because desired family size, as reported in surveys, remains close to or above the actual total fertility rate, meaning many Nigerien families are not yet choosing smaller families even where they have access to family planning services. Almost 70 percent of Niger’s population was under age 25 as of 2020, a direct consequence of sustained high fertility combined with falling child mortality.
Countries With the Highest Fertility Rates (Recent Estimates)
| Country | Total Fertility Rate | Year |
|---|---|---|
| Niger | 6.64-6.73 | 2022-2024 |
| Chad | ~6.1 | 2023 |
| Somalia | ~6.1 | 2023 |
| DR Congo | ~6.1 | 2023 |
| Central African Republic | high, above 6 | 2023 |
| Mali | high, above 6 | 2023-2024 |
Source: Statista, World Bank-sourced compilations, 2023-2025.
Where Families Are Smallest
South Korea holds the record for the lowest fertility rate ever measured for a country of its size, at 0.68 to 0.78 children per woman across recent estimates, having fallen from 0.81 in 2021 to 0.78 in 2022 and continuing to decline since.
South Korea remains the only OECD member with a rate below 1, well beneath the OECD average of 1.59 recorded in 2020 and far below the United States (1.64) and Japan (1.33) in the same comparison. South Korea, Hong Kong, Macau and Puerto Rico are among the very few places in the world with fertility below 1 according to World Bank data.
Countries With the Lowest Fertility Rates (Recent Estimates)
| Country/Territory | Total Fertility Rate | Year |
|---|---|---|
| South Korea | 0.68-0.78 | 2022-2025 |
| Hong Kong | below 1.0 | recent |
| Macau | below 1.0 | recent |
| Puerto Rico | below 1.0 | recent |
| Japan | 1.2-1.33 | 2020-2023 |
Source: World Bank; Statista compilations; Statistics Korea annual fertility reports.
South Korea’s own government has been explicit about the country’s trajectory: officials project the national population of 51 million could fall to below 38 million within four to five decades if the current fertility trend continues without substantial immigration, and the capital, Seoul, recorded an even lower birth rate of 0.59 in one recent measurement, below the already-record-low national average.
How Family Size Has Changed Historically
The global fertility transition, the multi-decade shift from large to small families that began in today’s wealthy countries and has since spread worldwide, followed a broadly similar path almost everywhere it has occurred: falling child mortality first reduced the practical need for large families as insurance against child death, followed by rising education, particularly for women, delayed marriage, and wider contraceptive access, each reinforcing the shift toward smaller intended and actual family sizes.
Why Family Size Is Changing
The drivers documented across country-level data are broadly consistent with those identified in the broader global fertility decline: expanding education and employment opportunities for women, delayed marriage and childbearing, wider contraceptive access, falling child mortality reducing the need for large families as insurance, rising housing and childcare costs in wealthier countries, and shifting cultural norms around ideal family size.
In Niger specifically, researchers note that persistently high desired fertility, not merely limited contraceptive access, remains a central obstacle to further decline, illustrating that preference change, not just access to family planning services, is often necessary before fertility falls substantially.
Desired Family Size Versus Actual Family Size
This is among the most important and most frequently overlooked distinctions in fertility research. In some high-fertility countries such as Niger, actual fertility runs below stated desired family size, meaning many women want more children than current economic and health conditions allow them to have and raise.
In many low-fertility countries, the reverse pattern holds: survey research in several European and East Asian countries has documented that many adults report wanting more children than they ultimately have, suggesting that at least part of below-replacement fertility reflects unmet reproductive intentions driven by economic and social constraints rather than a straightforward decline in the desire for children.
What Smaller Families Mean for Population Growth
South Korea’s trajectory demonstrates the long-run consequence of sustained very-low fertility with clarity: UN projections cited alongside South Korea’s own statistics see the country’s population more than halving by the end of the century absent a substantial shift in either fertility or immigration policy.
More broadly, the more than 90 countries where the World Bank and affiliated researchers estimate populations are not growing independent of immigration illustrate how widespread the low-fertility pattern has become, spanning much of Europe, parts of the Americas and increasingly Southeast Asia, even as high-fertility countries, concentrated overwhelmingly in Africa, continue to drive most of the world’s remaining population growth.
Frequently Asked Questions
1. What is the average family size worldwide?
The global total fertility rate stood at approximately 2.2 children per woman as of 2023-2024, down from about 5.3 in 1963, though this global average conceals an enormous range from below 1 in South Korea to nearly 7 in Niger.
2. Which country has the largest families?
Niger, with a total fertility rate estimated between 6.64 and 6.73 children per woman in recent data, the highest of any country, followed closely by Chad, Somalia and the Democratic Republic of the Congo.
3. Which country has the smallest families?
South Korea, with a fertility rate that fell to between 0.68 and 0.78 children per woman in recent years, the lowest sustained rate ever recorded for a country of its population size.
4. Why are family sizes shrinking?
Rising education and employment for women, delayed marriage and childbearing, wider contraceptive access, falling child mortality, and rising housing and childcare costs have combined to drive family size down across almost every country with sustained economic development.
5. How is family size measured?
Mainly through the total fertility rate, a period measure based on current age-specific birth rates, and separately through completed fertility or children ever born, which measures the actual lifetime number of children among women who have finished childbearing, typically assessed around age 45 to 49.
6. Do most high-fertility countries want smaller families?
Not necessarily. In Niger, for example, actual fertility runs below the desired family size reported in surveys, suggesting many families want more children than current conditions allow, the opposite pattern from many low-fertility countries where desired family size often exceeds actual fertility.
7. Is fertility declining everywhere?
Nearly everywhere, though at very different speeds. Of 31 countries where women had 4 or more children on average in 2023, 29 were in Africa, the last major region still completing its fertility transition, while more than 90 countries worldwide already have fertility too low to sustain population growth without immigration.
8. What happens to a country’s population when fertility stays very low for decades?
Population decline becomes increasingly likely absent substantial immigration. South Korea’s government-linked projections suggest its population of 51 million could fall below 38 million within four to five decades if current fertility trends continue.
9. Which European countries have the highest fertility rates?
Within the EU, France recorded the highest rate in a 2016 comparison at 1.92 births per woman, followed by Sweden (1.85) and Ireland (1.81), while Spain and Italy recorded the lowest at 1.34, all still well below the replacement level of 2.1.
10. Why does global population keep growing even as fertility falls?
Because falling fertility has been offset by longer life expectancy and sharply reduced child mortality, meaning more people are surviving into and through adulthood even as each generation has fewer children than the last, a pattern that is expected to reverse into population decline only later this century according to UN projections.
Sources
- World Bank, Total Fertility Rate data, as compiled in Statista’s “The State of Global Fertility”
- United Nations Department of Economic and Social Affairs, Population Division, World Fertility 2024
- Statistics Korea, annual fertility rate releases, 2021-2025
- CIA World Factbook, Niger country profile, demographic data
- Eurostat, fertility rate by EU country, 2016 comparison
- Statista, “Countries with the Lowest Fertility Rates 2025” and “Countries with the Highest Fertility Rate in 2024”
