Total fertility rate

The TFR for (say) year 2024 is usually computed by this formula: TFR_{2024} = 5 \times \left( \frac{\text{Number of births in 2024 by women aged 15 to 19}}{\text{Number of women in 2024 aged 15 to 19}} + \dots + \frac{\text{Number of births by women in 2024 aged 45 to 49}}{\text{Number of women in 2024 aged 45 to 49}}\right) . Ideally and more correctly, it should instead be computed by this formula: TFR_{2024} = \frac{\text{Number of births in 2024 by women aged 15}}{\text{Number of women in 2024 aged 15}} + \dots + \frac{\text{Number of births by women in 2024 aged 49}}{\text{Number of women in 2024 aged 49}} . But this second formula requires fertility rates for each single-year age group (which may not be available or may be poorly estimated). And so, government and international agencies usually prefer the first formula (which requires only fertility rates for each five-year age group). ==Related metrics==

Net reproduction rate An alternative measure of fertility is the net reproduction rate (NRR), which calculates the number of daughters a female would have in her lifetime if she were subject to prevailing age-specific fertility and mortality rates in a given year. When the NRR is exactly 1, each generation of females is precisely replacing itself. The NRR is not as commonly used as the TFR, but it is particularly relevant in cases where the number of male babies born is very high due to gender imbalance and sex selection. This is a significant consideration in world population dynamics, especially given the high level of gender imbalance in the heavily populated nations of China and India. The gross reproduction rate (GRR) is the same as the NRR, except that, like the TFR, it disregards life expectancy. Total period fertility rate The TFR, sometimes called TPFR—total period fertility rate, is a better index of fertility than the crude birth rate (annual number of births per thousand population) because it is independent of the age structure of the population, but it is a poorer estimate of actual completed family size than the total cohort fertility rate, which is obtained by summing the age-specific fertility rates that actually applied to each cohort as they aged through time. In particular, the TFR does not necessarily predict how many children young women now will eventually have, as their fertility rates in years to come may change from those of older women now. However, the TFR is a reasonable summary of current fertility levels. TFR and long term population growth rate, g, are closely related. For a population structure in a steady state, growth rate equals \log(\mathrm{TFR}/2)/X_m, where X_m is the mean age for childbearing women. Tempo effect The TPFR (total period fertility rate) is affected by a tempo effect—if age of childbearing increases, and life cycle fertility is unchanged, then while the age of childbearing is increasing, TPFR will be lower, because the births are occurring later, and then the age of childbearing stops increasing, the TPFR will increase, due to the deferred births occurring in the later period, even though the life cycle fertility has been unchanged. In other words, the TPFR is a misleading measure of life cycle fertility when childbearing age is changing, due to this statistical artifact. This is a significant factor in some countries, such as the Czech Republic and Spain in the 1990s. Some measures seek to adjust for this timing effect to gain a better measure of life-cycle fertility. Replacement rates Replacement fertility is the total fertility rate at which women give birth to enough babies to sustain population levels, assuming that mortality rates remain constant and net migration is zero. In 2003, the replacement fertility rate was 2.1 births per female for most developed countries (2.1 in the UK, for example), but could be as high as 3.5 in undeveloped countries because of higher mortality rates, especially child mortality. The global average for the replacement total fertility rate, eventually leading to a stable global population, for 2010–2015, was 2.3 children per female. ==Lowest-low fertility==

The term lowest-low fertility is defined as a TFR at or below 1.3. Lowest-low fertility was first noted within East Asian and European countries but recently spread to the Americas; the lowest rates are still found in East Asia. The East Asian American community in the United States also exhibits lowest-low fertility. At one point in the late 20th century and early 21st century this was also observed in Eastern and Southern Europe. However, the fertility rate then began to rise in most countries of Europe. Since the 2020s, however, TFR are falling again: in 2023, Spain's TFR fell to 1.19, and Italy's TFR fell to 1.2 children per woman. In Canada, the TFR in 2023 fell to its lowest ever recorded level, at 1.26 children per woman, with Statistics Canada reporting that Canada "has now joined the group of 'lowest-low' fertility countries". The lowest TFR recorded anywhere in the world in recorded history, is for the Xiangyang district of Jiamusi city (Heilongjiang, China) which had a TFR of 0.41 in 2000. In 2023, South Korea's TFR was 0.72 the world's lowest for that year. Outside Asia, the lowest TFR ever recorded was 0.80 for Eastern Germany in 1994. The low Eastern German value was influenced by a change to higher maternal age at birth, with the consequence that neither older cohorts (e.g. women born until the late 1960s), who often already had children, nor younger cohorts, who were postponing childbirth, had many children during that time. The total cohort fertility rate of each age cohort of women in East Germany did not drop as significantly. ==Population-lag effect==

A population that maintained a TFR of 3.8 over an extended period, without a correspondingly high death or emigration rate, would increase rapidly, doubling period ≈32 years. A population that maintained a TFR of 2.0 over a long time would decrease, unless it had a large enough immigration. It may take several generations for a change in the total fertility rate to be reflected in birth rate, because the age distribution must reach equilibrium. For example, a population that has recently dropped below replacement-level fertility will continue to grow, because the recent high fertility produced large numbers of young couples, who would now be in their childbearing years. This phenomenon carries forward for several generations and is called population momentum, population inertia, or population-lag effect. This time-lag effect is of great importance to the growth rates of human populations. TFR (net) and long-term population growth rate, g, are closely related. For a population structure in a steady state and with zero migration, g=\tfrac{\log(\text{TFR}/2)}{\text{X}_{m}}, where \text{X}_m is mean age for childbearing women and thus P(t) = P(0)^{(gt)}. At the left side is shown the empirical relation between the two variables in a cross-section of countries with the most recent y-y growth rate. The parameter \tfrac{1}{b} should be an estimate of the \text{X}_m; here equal to \tfrac{1}{0.02}=50 years, way off the mark because of population momentum. E.g. for {\log}(\tfrac{\text{TFR}}{2}) = 0, g should be exactly zero, which is seen not to be the case. ==Influencing factors==

for selected countries, 2011 has the highest TFR in the world at 6.73, in 2023. Fertility factors which determine the total fertility rate include social and economic inequality, wealth disparities, religiosity, social class, pension system, and overpopulation. ==National efforts to increase or decrease fertility==

Governments have often set population targets, to either increase or decrease the total fertility rate, or to have certain ethnic or socioeconomic groups have a lower or higher fertility rate. Often such policies have been interventionist, and abusive. The most notorious natalist policies of the 20th century include those in communist Romania and communist Albania, under Nicolae Ceaușescu and Enver Hoxha respectively. Conversely, in China the government sought to lower the fertility rate, and, as such, enacted the one-child policy (1978–2015), which included abuses such as forced abortions. In India, during the national emergency of 1975, a massive compulsory sterilization drive was carried out in India, but it is considered to be a failure and is criticized for being an abuse of power. Some governments have sought to regulate which groups of society could reproduce through eugenic policies, including forced sterilizations of population groups they considered undesirable. Such policies were carried out against ethnic minorities in Europe and North America in the first half of the 20th century, and more recently in Latin America against the Indigenous population in the 1990s; in Peru, former President Alberto Fujimori has been accused of genocide and crimes against humanity as a result of a sterilization program put in place by his administration targeting indigenous people (mainly the Quechua and Aymara people). Within these historical contexts, the notion of reproductive rights has developed. Such rights are based on the concept that each person freely decides if, when, and how many children to have - not the state or religion. According to the Office of the United Nations High Commissioner for Human Rights, reproductive rights "rest on the recognition of the basic rights of all couples and individuals to decide freely and responsibly the number, spacing and timing of their children and to have the information and means to do so, and the right to attain the highest standard of sexual and reproductive health. It also includes the right to make decisions concerning reproduction free of discrimination, coercion and violence, as expressed in human rights documents". ==History and future projections==

From around 10,000 BC to the beginning of the Industrial Revolution, fertility rates around the world were high by 21st-century standards, ranging from 4.5 to 7.5 children per woman. The onset of the Industrial Revolution around the year 1800 brought about what has come to be called the demographic transition. This eventually led to a long-term decline in TFR in every region of the world that has continued in the 21st century. 76-77 Child mortality could reach 50% and that plus the need to produce workers, male heirs, and old-age caregivers required a high fertility rate by 21st-century standards. To produce two adult children in this high mortality environment required at least four or more births. For example, fertility rates in Western Europe before 1800 ranged from 4.5 in Scandinavia to 6.2 in Belgium. Fertility rates in East Asia during this period were similar to those in Europe. 1800 to 1950 After 1800, the Industrial Revolution began in some places, particularly Great Britain, continental Europe, and the United States, and they underwent the beginnings of what is now called the demographic transition. Stage two of this process fueled a steady reduction in mortality rates due to improvements in public sanitation, personal hygiene and the food supply, which reduced the number of famines. There was a reduction in fertility rates, because there was simply no longer a need to birth so many children. The chart shows that the decline in the TFR since the 1960s has occurred in every region of the world. The global TFR is projected to continue declining for the remainder of the century, and reach a below-replacement level of 1.8 by 2100. Because the global fertility replacement rate for 2010–2015 was estimated to be 2.3, humanity has achieved or is approaching a significant milestone where the global fertility rate is equal to the global replacement rate. The average fertility rate in countries such as Thailand or Chile approached the mark of one child per woman, which triggered concerns about the rapid aging of populations worldwide. shows that after 1965, the demographic transition spread around the world, and the global TFR began a long decline that continues in the 21st century. ==By region==

countries, 2023 The United Nations Population Division divides the world into six geographical regions. The table below shows the estimated TFR for each region. Africa Africa has a TFR of 4.1, the highest in the world. In 2023, the most populous country in Africa, Nigeria, had an estimated TFR of 4.57. Within Africa, Sub-Saharan Africa has the highest fertility rate, with 27 out of the 30 countries with the highest fertility rates in the world being in Sub-Saharan Africa. As of 2021, 30% of all global births were in Sub-Saharan Africa. According to some estimates, by 2100 the share of the world's children born in sub-Saharan Africa will reach 55%, although other population projections suggest that fertility rates in Sub-Saharan Africa are declining faster than expected. Asia Eastern Asia Hong Kong, Macau, Singapore, South Korea, and Taiwan have the lowest-low fertility, defined as TFR at or below 1.3, and are among the lowest in the world. In 2018, North Korea had the highest TFR in East Asia, at 1.95. China implemented the one-child policy in January 1979 as a drastic population planning measure to control the ever-growing population at the time. In January 2016, the policy was replaced with the two-child policy. In July 2021, a three-child policy was introduced, as China's population is aging faster than almost any other country in modern history. Japan In 2022, Japan had a TFR of 1.26. Japan's population is rapidly aging due to both a long life expectancy and a low birth rate. The total population is shrinking, losing 430,000 in 2018, to a total of 126.4 million. Hong Kong and Singapore mitigate this through immigrant workers. In Japan, a serious demographic imbalance has developed, partly due to limited immigration to Japan. South Korea In South Korea, a low birthrate is one of its most urgent socio-economic challenges. Rising housing expenses, shrinking job opportunities for younger generations, insufficient support to families with newborns either from the government or employers are among the major explanations for its crawling TFR, which fell to 0.92 in 2019. Koreans are yet to find viable solutions to make the birthrate rebound, even after trying out dozens of programs over a decade, including subsidizing rearing expenses, giving priorities for public rental housing to couples with multiple children, funding day care centers, reserving seats in public transportation for pregnant women, and so on. In the past 20 years, South Korea has recorded some of the lowest fertility and marriage levels in the world. As of 2022, South Korea is the country with the world's lowest total fertility rate, at 0.78. In 2022, the TFR of the capital Seoul was 0.57. Southern Asia Bangladesh The fertility rate fell from 6.8 in 1970–1975, to 2.0 in 2020, an interval of about 47 years, or a little less than two generations. India The Indian fertility rate has declined significantly over the early 21st century. The Indian TFR declined from 5.2 in 1971 to 2.2 in 2018. The TFR in India declined to 2.0 in 2019–2020, marking the first time it has gone below replacement level.In 2026 it is estimated to be around 1.9 a significant decline. Iran In the Iranian calendar year (March 2019 – March 2020), Iran's total fertility rate fell to 1.8. Western Asia In 2023, the TFR of Turkey reached 1.51. Europe The average total fertility rate in the European Union (EU-27) was calculated at 1.53 children per female in 2021. In 2021, France had the highest TFR among EU countries at 1.84, followed by Czechia (1.83), Romania (1.81), Ireland (1.78) and Denmark (1.72). Latin America and the Caribbean In 2023, the TFR of Brazil, the most populous country in the region, was estimated at 1.75. United States The total fertility rate in the United States after World War II peaked at about 3.8 children per female in the late 1950s, dropped to below replacement in the early 1970s, and by 1999 was at 2 children. Currently, the fertility is below replacement among those native born, and above replacement among immigrant families, most of whom come to the US from countries with higher fertility. However, the fertility rate of immigrants to the US has been found to decrease sharply in the second generation, correlating with improved education and income. In 2021, the US TFR was 1.664, ranging between over 2 in some states and under 1.6 in others. Oceania Australia After World War II, Australia's TFR was approximately 3.0. In 2017, Australia's TFR was 1.74, i.e. below replacement. ==See also==