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Sub-replacement fertility

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Title: Sub-replacement fertility  
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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, plus a "third of a child" to make up for the higher probability of boys being born, infertility, individuals choosing not to have children, 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 (2015)
  7–8 Children
  6–7 Children
  5–6 Children
  4–5 Children
  3–4 Children
  2–3 Children
  1–2 Children

As of 2010, about 48% of the world population lives in nations with sub-replacement fertility.[3] 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, Brazil, Russia, Iran, Tunisia, China, 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.[4]


  • Causes 1
    • Higher education 1.1
    • Economic development 1.2
    • Urbanization 1.3
    • Contraception 1.4
    • Female social role 1.5
    • Government policies 1.6
    • Religiosity 1.7
    • Tempo effect 1.8
    • Partnership instability 1.9
  • Effects 2
  • Forecast 3
  • Cases of fertility rate increases in individual countries 4
    • United States 4.1
    • Other developed countries 4.2
  • See also 5
  • References 6
  • External links 7


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.

Higher education

The fact that more people are going to colleges and universities, and are working to obtain more post-graduate degrees there, along with the soaring costs of education, have contributed greatly to postponing marriage in many cases, and bearing children at all, or fewer numbers of children. And the fact that the number of women getting higher education has increased has contributed to fewer of them getting married younger, if at all. In the US, for example, females make up more than half of all college students, which is a reversal from a few decades back.[5]

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,.[6][7] 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.[8] 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.[8]

Female social role

Growing female participation in the work force has led to many women delaying or deciding against having children, or having fewer children. 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 India) have launched programmes to reduce fertility rates and curb population growth. (See One-child policy in China and Family planning in India.)


There are those who have pointed to the religiosity of the United States with its somewhat higher overall fertility rates as evidence of the influence of religion and human fertility. Some religious groups, such as Catholics, consider contraceptives to be sinful. Amish sects in the US, as well as among ultra orthodox Jews in Israel, very likely point to a high probability that the beliefs among certain religious groups, with their correspondingly higher fertility rates, indicate a causal effect among certain, though certainly not among all religious groups.[9]

Some others, though, claim that religiosity has been found to have virtually no causal relationship to fertility rates.[10][11][12][13][14]

Tempo effect

The conventionally reported measure of TFR, the period TFR (based on the level of fertility or number of births in a given year), is affected by 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 – assuming that the total number of births over a life cycle remains unchanged – 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 women in the past always had 1 child at the age of 20 (TFR of 1), and all women born in 1980 or later postponed having children until age 30 in the year 2000, there would be no births for 10 years (TFR of 0). After 10 years (assuming flat population structure, no deaths, etc.), in 2010, it would suddenly jump back up (TFR of 1), 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. For instance, this is computed to be the case in Spain in the period 1980–2002.[15]

John Bongaarts and Griffith Feeney have suggested that this tempo effect is driving the decline of measured fertility rate in the developed world.[16] Taking tempo changes into account, adjusted birth rates for a number of European countries are higher than the conventional TFR.[17] 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.[15]

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. [1] A study came to the result that instability of modern partnerships is a major cause of European sub-replacement fertility.[8]

Also, a number of sociologists and demographers have pointed out that among those who co-habit, without marrying, are now usually likely to have fewer children than those who are married, due to the lack of commitment in the male/female relationship. This uncertainty induces a 'wait and see' approach in many cases, especially on the part of the female.[18]


Old man at a nursing home in Norway.

Sub-replacement fertility does 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,[19] 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 believe the Earth's carrying capacity has already been exceeded and that even a stable population would not be sustainable.

The Greek historian Polybius largely blamed the decline of the Hellenistic world on low fertility rates, writing his work The Histories that: In a speech to Roman nobles, Julius Caesar commented on the low birthrates of the Roman elite: Upon the establishment of the Roman Empire, Emperor Augustus would introduce legislation to increase the birthrates of the Roman nobility.[22]

Some believe that not only the Great Recession, but the Great Depression, may have been the result of a decline in birthrates overall. Clarence L. Barber, an economist at the University of Manitoba, pointed out how demand for housing in the US, for example, began to decline in 1926, due to a decline in 'household formation' (marriage), due, he believed, to the effects of World War I upon society. In early 1929, US housing demand declined precipitously. And, of course, the stock market crash followed in October of that same year.[23]

Even though the overall world population continues to increase, it is more at the 'back end' than the 'front end' that this is occurring. That is, more people are kept alive than in the past due to improved nutrition, more refrigeration and better sanitation worldwide, as well as health care advances, from vaccines to antibiotics, and many other advances in medications and in different improvements in health care. Certainly, in advanced nations, few groups would be considered to be "breeding like rabbits". The 'baby boom' (1946–1964) in the US, was likely, if Barber's contentions are correct, more of a return to birthrates closer to historical norms, like those of the first decade of the 20th century (but the 'baby boom' of 1946–1964 were still lower than the 1900–1910 period), with birth dearths both before and since making the so-called "baby boom" appear so big.

Sub-replacement fertility can also change social relations in a society. Fewer children, combined with lower infant mortality has 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 the number of siblings, aunts and uncles and other extended family members.

Population aging may pose an economic challenge to governments as the number of retired citizens drawing public pensions rises in relation to the number of 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 birth and immigration rates. In France, payments to couples who have children have increased birth rates.[24]

Analysing data for 40 countries, Lee et al. show that fertility well above replacement and population growth would typically be most beneficial for government budgets. However, fertility near replacement and population stability would be most beneficial for standards of living when the analysis includes the effects of age structure on families as well as governments. And fertility moderately below replacement and population decline would maximize standards of living when the cost of providing capital for a growing labour force is taken into account.[25]


United Nation's population projections by location.
Note the vertical axis is logarithmic and represents millions of people.

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 1.9 in Britain and some other northern European countries, but the role of population policies in these trends is debated.[26]

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.

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.[27]

Cases of fertility rate increases in individual countries

United States

While much of the world has experienced declining fertility rates over the last twenty years, the total fertility rate in the United States has remained relatively stable.[28] 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 1.89, 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.[29]

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;[30] the United Kingdom where TFR increased from 1.64 in 2000 to 1.98 in 2010;[31][32] Australia, where the birth rate rose from 1.73 in 2001[33] to 1.93 in 2007[34] and New Zealand, where the TFR was 2.2 in 2008.[35]

Israel is the only developed country that has never had sub-replacement fertility; a declining Arab and Bedouin fertility rate is countered by religious Jewish groups (mostly Haredim) with higher than average fertility rates. In addition, the (mostly non-religious) aliyah Jews from the former USSR shifted from a 1 child per woman fertility rate to an average fertility rate close to 2.2 children per woman. As of 2008, Israel's Jewish fertility rate is the highest among the industrial nations.[36]

See also

Economic dynamics


  1. ^ a b , 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. ^ "Figure 8: Population by Total Fertility (millions)" in World Population Prospects, the 2010 Revision. United Nations, Department of Economic and Social Affairs, Population Division (2011)
  4. ^
  5. ^ Mother's Educational Level Influences Birth Rate
  6. ^
  7. ^
  8. ^ a b c
  9. ^
  10. ^ Completing the Fertility Transition. UN
  11. ^ Fertility, Contraception and Population Policies. Population Division, Department of Economic and Social Affairs, United Nations Secretariat. 25 April 2003
  12. ^
  13. ^ Dyson, Tim. "On the future of human fertility in India".
  14. ^ UN, Various Mongolia – European Community Strategy Paper 2007–2013
  15. ^ a b Tempo Effect and Adjusted TFR
  16. ^
  17. ^ European Demographic Data Sheet 2008
  18. ^ Fertility Differences between Married and Cohabiting Couples: A Switching Regression Analysis
  19. ^
  20. ^
  21. ^
  22. ^
  23. ^ [2]. Real gross housing expenditures on new units can be separated into two multiplicative components; housing starts and the real average investment per unit. 25 After estimating the determinants of each, Bolch, Fels, and McMahon examined the building hypothesis by simulating what would have been the case in each situation if a "normal" situation had occurred. 26 The result was overbuilding in the number of housing units from 1922 through 1929. They also found "overinvestment" per individual housing unit from 1921 to 1928 and conclude that excessive housing starts relative to family formation led to the sharp decline in housing construction at the end of the twenties. In their view the demographic changes in the twenties were the proximate causes of this. In a 1978 study Clarence Barber was even more emphatic on the importance of demographic changes, suggesting that these were the ultimate explanation of the Great Depression. 27 Basing his explanation on a Harrod-Domar growth model, Barber argues that the rapid decline in the population's growth rate disturbed that equilibrium, and this rapid fall in the natural growth rate initiated the depression
  24. ^
  25. ^
  26. ^ Suddenly, the old world looks younger. The Economist, 14 June 2007.
  27. ^ Guillemette, Yvan and Robson, William B.P. (September 2006) No Elixir of Youth: Immigration Cannot Keep Canada Young. C.D. Howe Institute
  28. ^
  29. ^
  30. ^ Tabc3 Tableau complémentaire 3 : Taux de fécondité par groupe d'âges.
  31. ^ Doughty, Steve (17 September 2012) British birth rate has soared to one of highest in Europe thanks to increase in migrants. Daily Mail
  32. ^
  33. ^
  34. ^
  35. ^
  36. ^

External links

  • List of countries by fertility – CIA World Factbook
  • World Factbook table of Total Fertility Rate ordered by country name
  • Four Surprises in Global Demography By Nicholas Eberstadt
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