Sub-replacement fertility

Sub-replacement fertility

Sub-replacement fertility is a total fertility rate (TFR) that (if sustained) leads to each new generation being less populous than the previous one in a given area. In developed countries sub-replacement fertility is any rate below approximately 2.1 children born per woman, but the threshold can be as high as 3.4 in some developing countries because of higher mortality rates.[1] Taken globally, the total fertility rate at replacement was 2.33 children per woman in 2003.[1] This can be "translated" as 2 children per woman to replace the parents, as well as a third to make up for infertile women and men, those who do not wish to have children, the higher probability of boys being born, and early mortality prior to the end of their fertile life.[2]

Replacement level fertility in terms of the net reproduction rate (NRR) is exactly one, because the NRR takes both mortality rates and sex ratios at birth into account.

Map of countries by fertility rate.
  7-8 Children
  6-7 Children
  5-6 Children
  4-5 Children
  3-4 Children
  2-3 Children
  1-2 Children
  0-1 Children

Today about 42% of the world population lives in nations with sub-replacement fertility.[citation needed] Nonetheless most of these countries still have growing populations due to immigration, population momentum and increase of the life expectancy. This includes most nations of Europe, Canada, Australia, Russia, Iran, Tunisia, China, Japan, and many others. The countries or areas that have the lowest fertility are Hong Kong, Macau, Singapore, Taiwan, Ukraine and Lithuania. Only a few countries have low enough or sustained sub-replacement fertility (sometimes combined with other population factors like emigration) to have population decline, such as Japan, Germany, Lithuania, and Ukraine.[3]



Graph of Total Fertility Rates vs. GDP per capita of the corresponding country, 2009. Only countries with over 5 Million population were plotted to reduce outliers. Sources: CIA World Fact Book

There have been a number of explanations for the general decline in fertility rates in much of the world, and the true explanation is almost certainly a combination of different factors.

Economic development

The growth of wealth and human development are related to this phenomenon (see the Demographic-economic paradox). High costs of living and job insecurity can make it difficult for young people to marry and start families.


The increase of urbanization around the world is considered by some a central cause. In recent times, residents of urban areas tend to have fewer children than people in rural areas,.[4][5] The need for extra labour from children on farms does not apply to urban-dwellers. Cities tend to have higher property prices, making a large family more expensive, especially in those societies where each child is now expected to have his own bedroom, rather than sharing with siblings as was the case until recently. Rural areas also tend to be more conservative with less contraception and abortion than urban areas.


Changes in contraception are also an important cause, and one that has seen dramatic changes in the last few generations. Legalization, and widespread acceptance, of contraception in the developed world is a large factor in decreased fertility levels. A systematic review, however, came to the result that European fertility rates do not seem to be decreased significantly by availability of contraception.[6] The other way around, the same review also stated that government support of assisted reproductive technology is beneficial for families, but its effect on total fertility rate in Europe is extremely small.[6]

Female social role

Growing female participation in the work force has led to many women delaying or deciding against having children, or to not have as many. A longer pursuit of education also delays marriages. Greater access to contraception and abortion, and greater proclivity of women to use them, also has reduced rates.

Other social changes both separate and related to feminism also have played a role. Bearing children is regarded as less of a social duty than it once was in many societies. Women's social status increasingly correlates with their work or behaviour as consumers rather than from their role as mothers. Indeed having a large family is often socially deprecated, being associated with lower status groups.

Government policies

Some governments (e.g. those of China and Iran) have launched programs to reduce fertility rates and curb population growth. (See One-child policy in China and Family planning in Iran.)


Religiousness have been found to have virtually no causal relationship to fertility rates. [7][8][9][10][11]

Tempo effect

In the conventionally reported measure of TFR, the period TFR (based on the level of fertility or number of births in a given year), there is a statistical effect called the tempo effect which makes it a misleading measure of overall (life cycle) fertility.

Specifically, if the age of childbearing increases – but assuming that the total number of births over a life cycle remains unchanged – then while this increase is happening, the measured TFR is lower (the births happen in a later year), but when the age of childbearing stops increasing the TFR increase, due to these births catching up. For illustration, if in the past women always had 1 child at the age of 20 (TFR of 1), but suddenly in the year 2000 all women born in 1980 or later postponed having children until age 30, there would suddenly be no births for 10 years (TFR of 0), and then 10 years later (2010) it would suddenly jump back up (TFR of 1) (assuming flat population structure, no deaths, etc.), even though the life cycle TFR was always 1.

Thus, period TFR reflects not only life cycle TFR, but also timing effects, and these effects are conflated in a simple period TFR number. Life cycle TFR is unambiguous, and strict measure of life cycle fertility are not affected by this effect (e.g., counting the average children that have been born to all women who cease child-bearing in a given year (via menopause, sterilization, death, etc.)), but are lagging statistics because they require women to cease child-bearing before they are counted. Thus, adjusted measures of TFR – period TFR, adjusted for timing – are proposed instead to give a more accurate measure of life cycle fertility, without needing to wait until women have definitively ceased bearing children.

Thus, if age of childbearing is increasing and life cycle fertility is decreasing, period TFR will initially overstate the decline, and then may have a spurious increase even if life cycle fertility is actually still declining. This is computed to be the case in Spain in the period 1980–2002, for instance.[12]

John Bongaarts and Griffith Feeney have suggested that this tempo effect is driving the decline of measured fertility rate in the developed world.[13] Taking tempo changes into account, adjusted birth rates for a number of European countries are higher than the conventional TFR.[14] A particularly strong example is the Czech Republic in the period 1992–2002, which witnessed a steady rise in childbearing age, hence the period TFR dropped sharply, overstating the decline in life cycle fertility.[12]

Partnership instability

Another explanation for falling fertility could be a reduction in the frequency of sex in populations with low birth rates. For example, according to a survey published by the Japanese Family Planning Association in March 2007, a record 39.7 per cent of Japanese citizens aged 16–49 had not had sex for more than a month.[2] A study came to the result that instability of modern partnerships is a major cause of European sub-replacement fertility.[6]


Sub-replacement fertility do not immediately translate into a population decline because of population momentum: recently high fertility rates produce a disproportionately young population, and younger populations have higher birth rates. This is why some nations with sub-replacement fertility still have a growing population, because a relatively large fraction of their population are still of child-bearing age. But if the fertility trend is sustained (and not compensated by immigration), it results in population ageing and population decline. This is forecast for most of the countries of Europe and East Asia.

Current estimates expect the world's total fertility rate to fall below replacement levels by 2050,[15] although population momentum will continue to increase global population for several generations beyond that. The promise of eventual population decline helps reduce concerns of overpopulation, but many[who?] believe the Earth's carrying capacity has already been exceeded and that even a stable population would not be sustainable.

Sub-replacement fertility can also change social relations in a society. Fewer children, combined with lower infant mortality has also made the death of children a far greater tragedy in the modern world than it was just fifty years ago. Having many families with only one or two children also reduces greatly the number of siblings, aunts and uncles.

Population aging poses an economic cost on societies, as the number of elderly retirees rises in relation to the number of young workers. This has been raised as a political issue in France, Germany, and the United States, where many people have advocated policy changes to encourage higher fertility and immigration rates. In France, payments to couples to have children have increased birthrate.[16]


Some European governments, fearful of a future pensions crisis, have developed natalist policies to attempt to encourage more women to have children. Measures include increasing tax allowances for working parents, improving child-care provision, reducing working hours/weekend working in female-dominated professions such as healthcare and a stricter enforcement of anti-discrimination measures to prevent professional women's promotion prospects being hindered when they take time off work to care for children. Over recent years, the fertility rate has increased to around 2.0 in France and 1.8 in Britain and some other northern European countries, but the role of population policies in these trends is debated.[17]

Attempts to increase the fertility rate among working women bring difficult political dilemmas: how far to alter traditional working practices so that women who are juggling work and child-raising responsibilities are not disadvantaged in their careers compared with men (for example, by legislating for compulsory paternity leave, flexible working and/or limiting total weekly working hours for men as well as women) and above all the question of whether the problem of sub-replacement fertility is so serious that unmarried women should also now be encouraged to have more children.

Giving women paid maternity leave can have the unintended negative consequence of dissuading employers from hiring women because they may fear having to pay a pregnant woman wages for a job she isn't doing. This may increase the gender-wage gap, the income disparity between men and women in the labor force. This disincentive can be ameliorated by giving parental leave to both men and women.

Germany’s family minister Ursula von der Leyen has stated that the slight increase[when?] in Germany, Italy, and other European countries with low fertility might be the first small steps to an eventual recovery.[citation needed] Although the increase will so far not counter an expected population decline it will however slow it down. European analysts hope, with the help of government incentives and large-scale change towards family-friendly policies, to stall the population decline and reverse it by around 2030, expecting that most of Europe will have a slight natural increase by then. C. D. Howe Institute, for example, tries to demonstrate that immigration can not be used to effectively counter population ageing.[18]

Cases of fertility rate increases in individual countries

United States

While almost all of the developed world, and many other nations, have seen plummeting fertility rates over the last twenty years, the United States' rates have remained stable and even slightly increased. This is largely due to the high fertility rate among communities such as Hispanics, but it is also because the fertility rate among non-Hispanic whites in the US, after falling to about 1.6 in the 1970s and early 1980s, had increased and is now around 1.9, or slightly below replacement level, rather than collapsing to the 1.3-1.5 level common in Europe.

New England has a rate similar to most Western European countries, while the South, Midwest, and border states have fertility rates considerably higher than replacement. States where The Church of Jesus Christ of Latter-day Saints has a strong presence, most notably Utah, also have higher-than-replacement fertility rates, especially among the LDS population. Heaton and Goodman (1985) found that LDS women average about one child more than women in other religious groups.[19]

Other developed countries

Some other developed countries are also experiencing an increase in their birth rate, including France, which recorded a TFR of over 2.00 in 2008,[20] Australia, where the birth rate rose from 1.73 in 2001[21] to 1.93 in 2007 [22] and New Zealand, where the TFR was 2.2 in 2008.[23] A few developed countries have never had sub-replacement fertility for reasons that are unique to the particular country. One example of that is Israel, where the growing Arab and religious Jewish populations (mostly Haredim) have high fertility rates, and the aliyah of Jews from the diaspora also contributes to Israel's population growth.

See also

Economic dynamics:


  1. ^ a b Espenshade TJ, Guzman JC, and Westoff CF (2003). "The surprising global variation in replacement fertility". Population Research and Policy Review 22 (5/6): 575. doi:10.1023/B:POPU.0000020882.29684.8e. , Introduction and Table 1, p. 580
  2. ^ For example in the United Kingdom in 2001 304,635 boys were born as opposed to 289,999 girls, and some of these girls will not survive to the end of their child bearing years. In future, therefore, the girls born in this year would have to have more than two children each to replace the total population. For a full explanation see ‘Replacement Fertility, What has it been and What does it mean?’ (PDF)
  3. ^ "International Data Base". United States Census Bureau. Retrieved 2007-09-30. 
  4. ^ . PMID 7718907. 
  5. ^ . PMID 9004364. 
  6. ^ a b c Eshre Capri Workshop, G. (2010). "Europe the continent with the lowest fertility". Human Reproduction Update 16 (6): 590–602. doi:10.1093/humupd/dmq023. PMID 20603286.  edit
  7. ^ UN, Completing the Fertility Transition PDF
  8. ^ UN, Fertility, Contraception and Population Policies PDF
  9. ^ Dyson, T. (2001a). "A partial theory of world development: the neglected role of the demographic transition in the shaping of modern society". International Journal of Population Geography 7 (2): 67–90. doi:10.1002/ijpg.215. 
  10. ^ Dyson, On the future of human fertility in India PDF
  11. ^ UN, Various Mongolia - European Community Strategy Paper 2007-2013
  12. ^ a b Tempo Effect and Adjusted TFR
  13. ^ Bongaarts, J. (2004) "The End of the Fertility Transition in the Developed World" in Population and Development Review, Volume 28 Issue 3, Pages 419-443
  14. ^ European Demographic Data Sheet 2008
  15. ^ "population trends (dynamically generated)". EarthTrends. World Resources Institute.,1955-1960,1960-1965,1965-1970,1970-1975,1975-1980,1980-1985,1985-1990,1990-1995,1995-2000,2000-2005,2045-2050&variable_ID=369&theme=4&cID=&ccID=0,1,6,2,3,5,8,7,4. Retrieved 2010-06-13. 
  16. ^ Moore, Molly. "As Europe Grows Grayer, France Devises a Baby Boom". The Washington Post. Retrieved May 24, 2010. 
  17. ^ Suddenly, the old world looks younger. The Economist, June 14th 2007.
  18. ^ Immigration (Guillemette_Robson).qxp
  19. ^ [1]
  20. ^ Tableau complémentaire 3 : Taux de fécondité par groupe d'âges
  21. ^ "FEATURE ARTICLE 2: RECENT INCREASES IN AUSTRALIA'S FERTILITY, Australian Bureau of Statistics".!OpenDocument. 
  22. ^ "3301.0 - Births, Australia, 2007, Australian Bureau of Statistics". 
  23. ^ Collins, Simon (February 19, 2009). "Baby boom goes against mothers' advice". The New Zealand Herald. Retrieved November 14, 2011. 

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