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In [[demography]], '''demographic transition''' is a phenomenon and theory whichin the [[Social science|social sciences]] refersreferring to the historical shift from high [[birth rate]]s and high [[Mortality rate|death rates]] to low birth rates and low death rates, as societies attain more technology, education (especially of [[female education|women]]), and [[economic development]].<ref name=":2">{{Cite web|title=Models of Demographic Transition [ Biz/ed Virtual Developing Country ]|url=https://web.csulb.edu/~gossette/classes/g460/DemTrans4.html|access-date=2021-06-16|website=web.csulb.edu}}</ref> The demographic transition has occurred in most of the world over the past two centuries, bringing the unprecedented population growth of the [[Malthusianism|post-Malthusian period]], then reducing birth rates and population growth significantly in all regions of the world. The demographic transition strengthens economic growth process bythrough three changes: (i)a reduced dilution of capital and land stock, (ii)an increased investment in human capital, and (iii)an increased size of the laborlabour force relative to the total population and changed age population distribution.<ref name="Unified Growth Theory">{{cite book|title=Unified Growth Theory|last1=Galor|first1=Oded|date=2011|publisher=Princeton University Press|isbn=9781400838868|___location=Princeton}}</ref> Although this shift has occurred in many [[Developed country|industrialized countries]], the theory and model are frequently imprecise when applied to individual countries due to specific social, political, and economic factors affecting particular populations.<ref name=":2" />

However, the existence of some kind of demographic transition is widely accepted in the social sciences because of the well-established historical [[Correlation and dependence|correlation]] linking dropping [[fertility]] to social and economic development.<ref name="Nature">{{cite journal |doi=10.1038/nature08230 |pmid=19661915 |title=Advances in development reverse fertility declines |journal=Nature |volume=460 |issue=7256 |pages=741–3 |year=2009 |last1=Myrskylä |first1=Mikko |last2=Kohler |first2=Hans-Peter |last3=Billari |first3=Francesco C. |bibcode=2009Natur.460..741M|s2cid=4381880 }}</ref> Scholars debate whether [[Industrialisation|industrialization]] and higher incomes [[Causation (sociology)|lead to]] lower population, or whether lower populations lead to industrialization and higher incomes. Scholars also debate to what extent various proposed and sometimes inter-relatedinterrelated factors such as higher [[per capita]] income, lower [[Mortality rate|mortality]], old-age security, and rise of demand for [[human capital]] are involved.<ref name=":3">{{cite journal|last1=Galor|first1=Oded|title=The demographic transition: causes and consequences|journal=Cliometrica|date=17 February 2011|volume=6|issue=1|pages=1–28|doi=10.1007/s11698-011-0062-7|pmid=25089157|pmc=4116081}}</ref> Human capital gradually increased in the second stage of the industrial revolution, which coincided with the demographic transition. The increasing role of human capital in the production process led to the investment of human capital in children by families, which may be the beginning of the demographic transition.<ref name="jstor.org">{{cite journal | last1 = Galor | first1 = Oded | author-link = Oded Galor | year = 2005 | title = The Demographic Transition and the Emergence of Sustained Economic Growth |journal = Journal of the European Economic Association | volume = 3 | issue = 2–3| pages = 494–504 | doi=10.1162/jeea.2005.3.2-3.494| hdl = 10419/80187 | url = https://www.econstor.eu/bitstream/10419/80187/1/481895825.pdf }}</ref>

==History==

The theory is based on an interpretation of [[demography|demographic]] history developed in 1930 by the American demographer [[Warren Thompson, demographer|Warren Thompson]] (1887–1973).<ref name=DemenyAndMcNicoll>{{cite encyclopedia|title=Warren Thompson|encyclopedia=Encyclopedia of Population|volume=2|pages=[https://archive.org/details/encyclopediaofpo0000unse/page/939 939–40]|publisher=[[Macmillan Publishers|Macmillan Reference]]|year=2003|isbn=978-0-02-865677-9|url-access=registration|url=https://archive.org/details/encyclopediaofpo0000unse/page/939}}</ref> [[Adolphe Landry]] of France made similar observations on demographic patterns and population growth potential around 1934.<ref name=":4">{{cite journal|last1=Landry|first1=Adolphe|title=Adolphe Landry on the Demographic transition Revolution|journal=Population and Development Review|date=December 1987|volume=13|issue=4|pages=731–740|doi=10.2307/1973031|jstor=1973031}}</ref> In the 1940s and 1950s [[Frank W. Notestein]] developed a more formal theory of demographic transition.<ref name="Woods2000">{{cite book|last=Woods|first=Robert|title=The Demography of Victorian England and Wales|url=https://books.google.com/books?id=75DZmQtybMwC&pg=PA18|date=2000-10-05|publisher=Cambridge University Press|isbn=978-0-521-78254-8|pages=18}}</ref> In the 2000s [[Oded Galor]] researched the "various mechanisms that have been proposed as possible triggers for the demographic transition, assessing their empirical validity, and their potential role in the transition from stagnation to growth."<ref name="jstor.org"/> In 2011, the [[unified growth theory]] was completed, the demographic transition becomes an important part in unified growth theory.<ref name="Unified Growth Theory"/> By 2009, the existence of a negative correlation between fertility and industrial development had become one of the most widely accepted findings in social science.<ref name="Nature" />

The [[Jews of Bohemia and Moravia]] were among the first populations to experience a demographic transition, in the 18th century, prior to changes in mortality or fertility in other [[European Jews]] or in Christians living in the [[Czech lands]].<ref>{{cite book |last1=Vobecka |first1=Jana |title=Demographic Avant-Garde: Jews in Bohemia between the Enlightenment and the Shoah |date=2013 |publisher=Central European University Press |isbn=978-615-5225-33-8 |page=xvi |language=en}}</ref> [[John Caldwell (demographer)]] explained fertility rates in the third world are not dependent on the spread of industrialization or even on economic development and also illustrates fertility decline is more likely to precede industrialization and to help bring it about than to follow it.<ref>{{cite journal|last1=John C|first1=Caldwell|date=1976|title=Toward A Retatement of Demographic Transition Theory |url=https://www.jstor.org/stable/1971615|journal=Population and Development Review |volume=2|issue=3|pages=321–366|doi=10.2307/1971615 |jstor=1971615 |url-access=subscription}}</ref>

[[John Caldwell (demographer)]] explained fertility rates in the third world are not dependent on the spread of industrialization or even on economic development and also illustrates fertility decline is more likely to precede industrialization and to help bring it about than to follow it.<ref>{{cite journal|last1=John C|first1=Caldwell|date=1976|title=Toward A Retatement of Demographic Transition Theory |url=https://www.jstor.org/stable/1971615|journal=Population and Development Review |volume=2|issue=3|pages=321–366|doi=10.2307/1971615 |jstor=1971615 }}</ref>

==Summary        ==

[[File:Demographic-TransitionOWID.png|thumb|381x381px|Demographic transition overview, where "stage 5" is shown as unknown]]

The transition involves four stages, or possibly five.

* In stage one, [[pre-industrial society]], [[Mortality rate|death rates]] and [[birth rate]]s are high and roughly in balance. All human [[population]]s are believed to have had this balance until the late 18th century, when this balance ended in Western Europe.<ref name=":5">{{Cite web |last=Montgomery |first=Keith |title=Demographic Transition |url=http://pages.uwc.edu/keith.montgomery/demotrans/demtran.htm |website=WayBackMachine|archive-url=https://web.archive.org/web/20190605095831/http://pages.uwc.edu/keith.montgomery/demotrans/demtran.htm |websitearchive-date=WayBackMachine5 June 2019 }}</ref> In fact, growth rates were less than 0.05% at least since the [[Neolithic Revolution|Agricultural Revolution]] over 10,000 years ago.<ref name=":5" /> [[Population growth]] is typically very slow in this stage, because the society is constrained by the available food supply; therefore, unless the society develops new technologies to increase food production (e.g. discovers new sources of food or achieves higher crop yields), any fluctuations in birth rates are soon matched by death rates.

* In stage two, that of a [[developing country]], the [[Mortality rate|death rates]] drop quickly due to improvements in food supply and [[sanitation]], which increase [[life expectancy]] and reduce [[disease]]. The improvements specific to food supply typically include selective breeding and crop rotation and farming techniques.<ref name=":5" /> Numerous improvements in public health reduce mortality, especially childhood mortality.<ref name=":5" /> Prior to the mid-20th century, these improvements in public health were primarily in the areas of food handling, water supply, sewage, and personal hygiene.<ref name=":5" /> One of the variables often cited is the increase in female literacy combined with public health education programs which emerged in the late 19th and early 20th centuries.<ref name=":5" /> In [[Europe]], the death rate decline started in the late 18th century in [[northwestern Europe]] and spread to the south and east over approximately the next 100 years.<ref name=":5" /> Without a corresponding fall in birth rates this produces an [[Demographic trap|imbalance]], and the countries in this stage experience a large increase in [[population]].

* In stage three, birth rates fall due to various [[Fertility factor (demography)|fertility factors]] such as access to [[contraception]], increases in wages, [[urbanization]], a reduction in [[subsistence agriculture]], an increase in the status and education of women, a reduction in the value of children's work, an increase in parental investment in the education of children, and other social changes. Population growth begins to level off. The birth rate decline in developed countries started in the late 19th century in northern Europe.<ref name=":5" /> While improvements in contraception do play a role in birth rate decline, contraceptives were not generally available nor widely used in the 19th century and as a result likely did not play a significant role in the decline then.<ref name=":5" /> It is important to note that birth rate decline is caused also by a transition in values;, not just because of the availability of contraceptives.<ref name=":5" />

* DuringIn stage four, there are both low birth rates and low death rates. Birth rates may drop to well below replacement level, as has happened in countries like [[Germany]], [[Italy]], and [[Japan]], leading to a [[population decline|shrinking population]], a threat to many industries that rely on population growth. As the large group born during stage two ages, it creates an economic burden on the shrinking working population. Death rates may remain consistently low or increase slightly due to increases in lifestyle diseases due to low exercise levels and high [[obesity]] rates and an aging population in [[developed countries]]. By the late 20th century, birth rates and death rates in developed countries leveled off at lower rates.<ref name="geography.about.com">{{Citation | publisher = About | title = Geography | url = http://geography.about.com/od/culturalgeography/a/demotransition.htm | contribution = Demographic transition | access-date = 2010-10-26 | archive-date = 2017-02-26 | archive-url = https://web.archive.org/web/20170226225454/http://geography.about.com/od/culturalgeography/a/demotransition.htm | url-status = dead }}.</ref>

* Some scholars break out, from stage four, a "stage five" of below-replacement fertility levels. Others hypothesize a different "stage five" involving an increase in fertility.<ref name=bbc_sure>[https://www.bbc.co.uk/news/technology-19923200 Can we be sure the world's population will stop rising?], BBC News, 13 October 2012</ref>

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=== Stage one ===

In pre-industrial society, death rates and birth rates were both high, and fluctuatedfluctuating rapidly according to natural events, such as drought and disease, to produce a relatively constant and young population.<ref name=":2" /> [[Family planning]] and contraception were virtually nonexistent; therefore, birth rates were essentially only limited by the ability of women to bear children. Emigration depressed death rates in some special cases (for example, Europe and particularly the Eastern United States during the 19th century), but, overall, death rates tended to match birth rates, often exceeding 40 per 1000 per year. Children contributed to the economy of the household from an early age by carrying water, firewood, and messages, caring for younger siblings, sweeping, washing dishes, preparing food, and working in the fields.<ref>{{cite web|url=http://geographyfieldwork.com/DemographicTransition.htm|title=Demographic Transition Model| website=geographyfieldwork.com}}</ref> Raising a child cost little more than feeding him or her; there were no education or entertainment expenses. Thus, the total [[Cost of raising a child| cost of raising children]] barely exceeded their contribution to the household. In addition, as they became adults they became a major input to the family business, mainly farming, and were the primary form of insurance for adults in old age. In India, an adult son was all that prevented a widow from falling into destitution. While death rates remained high there was no question as to the need for children, even if the means to prevent them had existed.<ref name=Caldwell5>Caldwell (2006), Chapter 5</ref>

During this stage, the society evolves in accordance with [[Malthusian growth model| Malthusian]] paradigm, with population essentially determined by the food supply. Any fluctuations in food supply (either positive, for example, due to technology improvements, or negative, due to droughts and pest invasions) tend to translate directly into population fluctuations. [[Famine]]s resulting in significant mortality are frequent. Overall, [[population dynamics]] during stage one are comparable to those of animals living in the wild. This is the earlier stage of demographic transition in the world and also characterized by primary activities such as small fishing activities, farming practices, pastoralism, and petty businesses.

===Stage two===

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[[File:Angola population pyramid 2005.svg|right|upright=1.7|thumb| [[Population pyramid]] of [[Angola]] 2005]]

Another characteristic of Stage Two of the demographic transition is a change in the [[population pyramid|age structure]] of the population. In Stage One, the majority of deaths are concentrated in the first 5–10 years of life. Therefore, more than anything else, the decline in death rates in Stage Two entails the increasing survival of children and a growing population. Hence, the age structure of the population becomes increasingly youthful and start to have big families and more of these children enter the reproductive cycle of their lives while maintaining the high fertility rates of their parents. The bottom of the "[[population pyramid|age pyramid]]" widens first where children, teenagers and infants are here, accelerating population growth rate. The age structure of such a population is illustrated by using an example from the [[Third World]] today.

===Stage three===

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* In rural areas continued decline in childhood death meant that at some point parents realized that they did not need as many children to ensure a comfortable old age. As childhood death continues to fall and incomes increase, parents can become increasingly confident that fewer children will suffice to help in family business and care for them at old age.

* Increasing [[urbanization]] changes the traditional values placed upon fertility and the value of children in rural society. Urban living also raises the cost of dependent children to a family. A recent theory suggests that urbanization also contributes to reducing the birth rate because it disrupts optimal mating patterns. A 2008 study in Iceland found that the most fecund marriages are between distant cousins. Genetic incompatibilities inherent in more distant out breeding makes reproduction harder.<ref>{{Citation | title= Third Cousins Have Greatest Number Of Offspring, Data From Iceland Shows | url= https://www.sciencedaily.com/releases/2008/02/080207140855.htm | archive-url= https://web.archive.org/web/20210102112300/https://www.sciencedaily.com/releases/2008/02/080207140855.htm | url-status= dead | archive-date= 2 January 2021 | journal= ScienceDaily | date = 8 February 2008}}.</ref>

* In both rural and urban areas, the cost of children to parents is exacerbated by the introduction of compulsory education acts and the increased need to educate children so they can take up a respected position in society. Children are increasingly prohibited under law from working outside the household and make an increasingly limited contribution to the household, as school children are increasingly exempted from the expectation of making a significant contribution to domestic work. Even in equatorial Africa, children (under the age underof 5) are now required to have clothes and shoes, and may even requireneed school uniforms. Parents begin to consider it a duty to buy children('s) books and toys,. partlyPartly due to education and access to family planning, people begin to reassess their need for children and their ability to raise them.<ref name=Caldwell5/>

[[File:Familyplanningmalaysia.jpg|thumb|right|upright=1.15|A major factor in reducing birth rates in stage&nbsp;3 countries such as Malaysia is the availability of family planning facilities, like this one in Kuala Terengganu, Terengganu, Malaysia.]]

* Increasing literacy and employment lowers the uncritical acceptance of childbearing and motherhood as measures of the status of women. Working women have less time to raise children; this is particularly an issue where fathers traditionally make little or no contribution to child-raising, such as [[southern Europe]] or [[Japan]]. Valuation of women beyond childbearing and motherhood becomes important.

* Improvements in contraceptive technology are now a major factor. Fertilityin fertility decline. is caused as much by changesChanges in values aboutregarding children and gender play as bysignificant a role as the availability of contraceptives and knowledge of how to use them.

The resulting changes in the age structure of the population include a decline in the youth [[dependency ratio]] and eventually [[population aging]]. The population structure becomes less triangular and more like an elongated balloon. During the period between the decline in youth dependency and rise in old age dependency there is a [[demographic window]] of opportunity that can potentially produce economic growth through an increase in the ratio of working age to dependent population; the [[demographic dividend]].

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[[File:Argentina_2022_population_pyramid.svg|thumb|Population pyramid of [[Demographics of Argentina|Argentina]] in 2022 (Stage four).]]

This occurs where birth and death rates are both low, leading to a total population stability. Death rates are low for a number of reasons, primarily due to lower rates of diseases and higherincreased food production of food. The birth rate is low because people have more opportunities to choose if they want children;. thisThis is made possible by improvements in contraception or women gaining more independence and work opportunities.<ref>{{Citation | url = http://www.main-vision.com/richard/demographic.htm | title = Main vision |contribution = Demographic}}.</ref> The DTM (Demographic Transition model) is only a suggestion about the future population levels of a country, not a prediction.

Countries that were at this stage ([[total fertility rate]] between 2.0 and 2.5) in 2015 include: Antigua and Barbuda, Argentina, Bahrain, Bangladesh, Bhutan, Cabo Verde, El Salvador, Faroe Islands, Grenada, Guam, India, Indonesia, Kosovo, Libya, Malaysia, Maldives, Mexico, Myanmar, Nepal, New Caledonia, Nicaragua, Palau, Peru, Seychelles, Sri Lanka, Suriname, Tunisia, Turkey, and Venezuela.<ref>{{cite web|url=https://data.worldbank.org/indicator/SP.DYN.TFRT.IN|title=Fertility rate, total (births per woman) - Data|website=data.worldbank.org}}</ref>

===Stage five===

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Some countries have [[sub-replacement fertility]] (that is, below 2.1–2.2 children per woman). Replacement fertility is generally slightly higher than 2 (the level which replaces the two parents, achieving equilibrium) both because boys are born more often than girls (about 1.05–1.1 to 1), and to compensate for deaths prior to full reproduction. Many European and East Asian countries now have higher death rates than birth rates. [[Population aging]] and [[population decline]] may eventually occur, assuming that the fertility rate does not change and sustained mass immigration does not occur.

Using data through 2005, researchers have suggested that the negative relationship between development, as measured by the [[Human Development Index]] (HDI), and birth rates had reversed at very high levels of development. In many countries with very high levels of development, fertility rates were approaching two children per woman in the early 2000s.<ref name="Nature" /><ref>{{Citation | title= The best of all possible worlds? | url = https://www.economist.com/science-and-technology/2009/08/06/the-best-of-all-possible-worlds | newspaper = The Economist | date = 6 August 2009}}.</ref> However, fertility rates declined significantly in many very high development countries between 2010 and 2018, including in countries with high levels of [[gender parity]]. The global data no longer support the suggestion that fertility rates tend to broadly rise at very high levels of national development.<ref name=":1">{{Cite journal|last=Gaddy|first=Hampton Gray|date=2021-01-20|title=A decade of TFR declines suggests no relationship between development and sub-replacement fertility rebounds|url=https://www.demographic-research.org/volumes/vol44/5/|journal=Demographic Research|language=en|volume=44|pages=125–142|article-number=5 |doi=10.4054/DemRes.2021.44.5|issn=1435-9871|doi-access=free}}</ref>

From the point of view of [[evolutionary biology]], wealthier people having fewer children is unexpected, as [[natural selection]] would be expected to favor individuals who are willing and able to convert plentiful resources into plentiful fertile descendants. This may be the result of a departure from the [[Evolutionary psychology#Environment of evolutionary adaptedness|environment of evolutionary adaptedness]].<ref name=bbc_sure /><ref>{{cite journal | last1 = Clarke | first1 = Alice L. | last2 = Low | first2 = Bobbi S. | year = 2001 | title = Testing evolutionary hypotheses with demographic data |journal = Population and Development Review | volume = 27 | issue = 4| pages = 633–660 | doi=10.1111/j.1728-4457.2001.00633.x| url = https://deepblue.lib.umich.edu/bitstream/2027.42/74296/1/j.1728-4457.2001.00633.x.pdf | hdl = 2027.42/74296| hdl-access = free }}</ref><ref>{{cite journal |last1=Daly |first1= Martin |last2=Wilson |first2=Margo I |title=Human evolutionary psychology and animal behaviour |journal= Animal Behaviour |url= http://courses.washington.edu/evpsych/Daly%26Wilson-HEP-AB1999.pdf |publisher= Department of Psychology, McMaster University |access-date=14 November 2018 |date=26 June 1998|volume= 57 |issue= 3 |pages= 509–519 |doi= 10.1006/anbe.1998.1027 |pmid= 10196040 |s2cid= 4007382 }}</ref>

Most models posit that the birth rate will stabilize at a low level indefinitely. Some dissenting scholars note that the modern environment is exerting [[evolutionary pressure]] for higher fertility, and that eventually due to individual natural selection or cultural selection, birth rates may rise again. Part of the "cultural selection" hypothesis is that the variance in birth rate between cultures is significant; for example, some religious cultures have a higher birth rate that is not accounted for by differences in income.<ref>{{cite journal|last1=Kolk|first1=M.|last2= Cownden |first2=D.|last3=Enquist|first3=M. |title=Correlations in fertility across generations: can low fertility persist?|journal=Proceedings of the Royal Society B: Biological Sciences|date=29 January 2014|volume=281|issue=1779|page = 20132561 |doi=10.1098/rspb.2013.2561|pmid= 24478294 |pmc=3924067}}</ref><ref>{{cite journal|last1=Burger|first1=Oskar|last2= DeLong|first2=John P.|title= What if fertility decline is not permanent? The need for an evolutionarily informed approach to understanding low fertility|journal= Philosophical Transactions of the Royal Society B: Biological Sciences|date=28 March 2016|volume=371|issue=1692|page = 20150157|doi= 10.1098/rstb.2015.0157 |pmid= 27022084|pmc= 4822437}}</ref><ref>{{cite news |title= Population paradox: Europe's time bomb |url= https://www.independent.co.uk/news/world/europe/population-paradox-europes-time-bomb-888030.html |access-date=31 March 2019 |work=The Independent |date=9 August 2008}}</ref> In his book ''Shall the Religious Inherit the Earth?'', [[Eric Kaufmann]] argues that demographic trends point to religious fundamentalists greatly increasing as a share of the population over the next century.<ref>{{Cite web|title=Shall the religious inherit the earth?|url=https://www.mercatornet.com/articles/view/shall_the_religious_inherit_the_earth/|date=April 6, 2010|website=Mercator Net|access-date=February 27, 2020|archive-date=June 23, 2019|archive-url=https://web.archive.org/web/20190623040350/https://www.mercatornet.com/articles/view/shall_the_religious_inherit_the_earth/|url-status=dead}}</ref><ref>{{Cite journal|last=McClendon|first=David|date=Autumn 2013|title=Shall the Religious Inherit the Earth? Demography and Politics in the Twenty-First Century, by ERIC KAUFMANN|url=https://academic.oup.com/socrel/article-abstract/74/3/417/1640161|journal=Sociology of Religion|volume=74|issue=3|pages=417–9|doi=10.1093/socrel/srt026|url-access=subscription}}</ref>

[[Jane Falkingham]] of [[Southampton University]] has noted that "We've actually got population projections wrong consistently over the last 50 years... we've underestimated the improvements in mortality... but also we've not been very good at spotting the trends in fertility."<ref name= bbc_sure /> In 2004 a United Nations office published its guesses for global population in the year 2300; estimates ranged from a "low estimate" of 2.3 billion (tending to −0.32% per year) to a "high estimate" of 36.4 billion (tending to +0.54% per year), which were contrasted with a deliberately "unrealistic" illustrative "constant fertility" scenario of 134 trillion (obtained if 1995–2000 fertility rates stay constant into the far future).<ref name= bbc_sure /><ref>{{cite web|title= World Population to 2300|url= https://www.un.org/esa/population/publications/longrange2/WorldPop2300final.pdf |publisher=United Nations Department of Economic and Social Affairs |access-date= 24 May 2016|date= 2004}}</ref>

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==Effects on age structure==

[[File:Dtm pyramids.png|thumb|upright=1.4|One such visualization of this effect may be approximated by these hypothetical population pyramids.]]

The decline in death rate and birth rate that occurs during the demographic transition may transform the age structure. When the death rate declines during the second stage of the transition, the result is primarily an increase in the younger population. TheThis reasonis being thatbecause when the death rate is high (stage one), the infant mortality rate is very high, often above 200 deaths per 1000 children born. WhenAs the death rate falls or improves, this may includelead to a lower infant mortality rate and increased child survival.

Over time, as individuals with increased survival rates age, there may also be an increase in the number of older children, teenagers, and young adults. This implies that there is an increase in the fertile population proportion which, with constant [[Total fertility rate|fertility rates]], may lead to an increase in the number of children born. This will further increase the growth of the child population. The second stage of the demographic transition, therefore, implies a rise in child dependency and creates a [[Population pyramid#Youth bulge|youth bulge]] in the population structure.<ref name=":0">{{Cite book|title=Population: An Introduction to Concepts and Issues|last=Weeks|first=John R.|publisher=Cengage Learning|year=2014|isbn=978-1-305-09450-5|pages=94–97}}</ref>

As a population continues to move through the demographic transition into the third stage, fertility declines and the youth bulge prior to the decline ages out of child dependency into the working ages. This stage of the transition is often referred to as the golden age, and is typically when populations see the greatest advancements in living standards and economic development.<ref name=":0" /> However, further declines in both mortality and fertility will eventually result in an aging population, and a rise in the [[Age Dependency Ratio|aged dependency ratio]]. An increase of the aged dependency ratio often indicates that a population has reached below replacement levels of [[fertility]], and as result does not have enough people in the working ages to support the economy, and the growing dependent population.<ref name=":0" />

==Historical studies==

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France displays real divergences from the standard model of Western demographic evolution. The uniqueness of the French case arises from its specific demographic history, its historic cultural values, and its internal regional dynamics. France's demographic transition was unusual in that the mortality and the natality decreased at the same time, thus there was no demographic boom in the 19th century.<ref>{{cite journal |title=Quand l'Angleterre rattrapait la France|url=https://www.ined.fr/en/publications/population-and-societies/quand-l-angleterre-rattrapait-la-france-en/|journal=Population & Sociétés |date=May 1999 |issue=346 |first1= Jacques |last1=Vallin|first2=Graziella |last2=Caselli |language=fr}}</ref>

France's demographic profile is similar to its European neighbors and to developed countries in general, yet it seems to be staving off the population decline of Western countries. With 62.9 million inhabitants in 2006, it was the second most populous country in the European Union, and it displayed a certain demographic dynamism, with a growth rate of 2.4% between 2000 and 2005, above the European average. More than two-thirds of that growth can be ascribed to a natural increase resulting from high fertility and birth rates. In contrast, France is one of the developed nations whose migratory balance is rather weak, which is an original feature at the European level. Several interrelated reasons account for such singularities, in particular the impact of pro-family policies accompanied by greater unmarried households and out-of-wedlock births. These general demographic trends parallel equally important changes in regional demographics.

Since 1982, the same significant tendencies have occurred throughout mainland France: demographic stagnation in the least-populated rural regions and industrial regions in the northeast, with strong growth in the southwest and along the Atlantic coast, plus dynamism in metropolitan areas. Shifts in population between regions account for most of the differences in growth. The varying demographic evolution regions can be analyzed though the filter of several parameters, including residential facilities, economic growth, and urban dynamism, which yield several distinct regional profiles. The distribution of the French population therefore seems increasingly defined not only by interregional mobility but also by the residential preferences of individual households.

These challenges, linked to configurations of population and the dynamics of distribution, inevitably raise the issue of town and country planning. The most recent census figures show that an outpouring of the urban population means that fewer rural areas are continuing to register a negative migratory flow – two-thirds of rural communities have shown some since 2000. The spatial demographic expansion of large cities amplifies the process of [[Peri-urbanisation|peri-urbanization]] yet is also accompanied by movement of selective residential flow, social selection, and sociospatial segregation based on income.<ref>{{Citation | first1 = Guy | last1 = Baudelle | first2 = David | last2 = Olivier | title= Changement Global, Mondialisation et Modèle De Transition Démographique: réflexion sur une exception française parmi les pays développés | journal= Historiens et Géographes | year = 2006 | volume = 98 | issue = 395 | pages = 177–204 | issn = 0046-757X | language = fr}}</ref>

===Asia===

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====China====

China experienced a demographic transition with high death rate and low fertility rate from 1959 to 1961 due to the great famine.<ref name=":3" /> However, as a result of the economic improvement, the birth rate increased and mortality rate declined in China before the early 1970s.<ref name=":4" /> In the 1970s, China's birth rate fell at an unprecedented rate, which had not been experienced by any other population in a comparable time span. The birth rate fell from 6.6 births per women before 1970 to 2.2 births per women in 1980.The rapid fertility decline in China was caused by government policy: in particular the "later, longer, fewer" policy of the early 1970s and in the late 1970s the one-child policy was also enacted which highly influence China demographic transition.<ref>{{cite journal|last1=John|first1=Bongaarts|last2=Susan|first2=Greenhalgh|date=1985|title=An alternative to the One-Child Policy in China|url=https://www.jstor.org/stable/1973456|journal=Population and Development Review|volume=11|issue=4|pages=585–617|doi=10.2307/1973456 |jstor=1973456 |url-access=subscription}}</ref> As the demographic dividend gradually disappeared, the government abandoned the one-child policy in 2011 and fully lifted the two-child policy from 2015.The two-child policy has had some positive effects on the fertility which causes fertility constantly to increase until 2018.However fertility started to decline after 2018 and meanwhile there was no significant change in mortality in recent 30 years.

===Madagascar===

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Russia entered stage two of the transition in the 18th century, simultaneously with the rest of Europe, though the effect of transition remained limited to a modest decline in death rates and steady population growth. The population of Russia nearly quadrupled during the 19th century, from 30 million to 133 million, and continued to grow until the First World War and the turmoil that followed.<ref>{{cite web|url=http://www.tacitus.nu/historical-atlas/population/russia.htm|title=Population of Eastern Europe|website=tacitus.nu|access-date=2015-09-30|archive-date=2018-01-08|archive-url=https://web.archive.org/web/20180108232321/http://www.tacitus.nu/historical-atlas/population/russia.htm|url-status=dead}}</ref> Russia then quickly transitioned through stage three. Though fertility rates rebounded initially and almost reached 7 children/woman in the mid-1920s, they were depressed by the 1931–33 famine, crashed due to the Second World War in 1941, and only rebounded to a sustained level of 3 children/woman after the war. By 1970 Russia was firmly in stage four, with crude birth rates and crude death rates on the order of 15/1000 and 9/1000 respectively. Bizarrely, however, the birth rate entered a state of constant flux, repeatedly surpassing the 20/1000 as well as falling below 12/1000.

In the 1980s and 1990s, Russia underwent a unique demographic transition; observers call it a "demographic catastrophe": the number of deaths exceeded the number of births, life expectancy fell sharply (especially for males) and the number of suicides increased.<ref>{{Citation | editor-first = George J | editor-last = Demko | others = et al | title = Population under Duress: The Geodemography of Post-Soviet Russia | year = 1999 | url = | publisher = Westview Press |isbn=0813389399 }}{{ISBN?}}{{page needed|date=July 2021}}</ref> From 1992 through 2011, the number of deaths exceeded the number of births; from 2011 onwards, the opposite has been the case.

=== United States ===

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DTM assumes that the birth rate is independent of the death rate. Nevertheless, demographers maintain that there is no historical evidence for society-wide fertility rates rising significantly after high mortality events. Notably, some historic populations have taken many years to replace lives after events such as the [[Black Death]].

Some have claimed that DTM does not explain the early fertility declines in much of Asia in the second half of the 20th century or the delays in fertility decline in parts of the Middle East. Nevertheless, the demographer [[John Caldwell (demographer)|John C. Caldwell]] has suggested that the reason for the rapid decline in fertility in some [[developing country|developing countries]] compared to Western Europe, the United States, Canada, Australia and New Zealand is mainly due to government programs and a massive investment in education both by governments and parents.<ref name=Caldwell10/>

DTM does not well explain the impact of government policies on birth rate. In some developing countries, governments often implement some policies to control the growth of fertility rate. China, for example, underwent a fertility transition in 1970, and the Chinese experience was largely influenced by government policy. In particular the "later, longer, fewer" policy of 1970 and one birth policy was enacted in 1979 which all encouraged people to have fewer children in later life. The fertility transition indeed stimulated economic growth and influenced the demographic transition in China.<ref>{{cite journal|last1=Carl-johan|first1=dalgaard|last2=pablo|first2=selaya|date=2015|title=Climate and the Emergence of Global Income|url=https://www.jstor.org/stable/26160242|journal=The Review of Economic Studies|volume=83|issue=4|pages=1334–1363|jstor=26160242 }}</ref>

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The Second Demographic Transition (SDT) is a conceptual framework first formulated in 1986 by Ron Lesthaeghe and [[Dick van de Kaa|Dirk van de Kaa]].<ref name="Lesthaeghe_2011">{{citation |author=Ron J. Lesthaeghe |date=2011 |title=The "second demographic transition": a conceptual map for the understanding of late modern demographic developments in fertility and family formation |journal=Historical Social Research |volume=36 |number=2 |pages=179–218 |url=http://nbn-resolving.de/urn:nbn:de:0168-ssoar-342259}}</ref>{{rp|181}}<ref name="Lesthaeghe_2011"/><ref name="Bevolking">{{cite book|author1=Ron Lesthaeghe |author2=Dirk van de Kaa|author-link2=Dick van de Kaa|title=Bevolking: groei en krimp [Population: growth and shrinkage]|date=1986|publisher=Deventer : Van Loghum Slaterus|isbn=9789036800181|pages=9–24|chapter=Twee demografische transities? [Second Demographic Transition]}}(in Dutch with summaries in English)</ref><ref name="Lesthaeghe_1991">{{citation |author=Ron J. Lesthaeghe |date=1991 |title=The Second Demographic Transition in Western countries: An interpretation |url=https://www.researchgate.net/publication/257928736 |format=PDF |series=IPD Working Paper, Interuniversity Programme in Demography |access-date=February 26, 2017}}</ref> SDT addressed the changes in the patterns of sexual and reproductive behavior which occurred in North America and Western Europe in the period from about 1963, when the [[combined oral contraceptive pill|birth control pill]] and other cheap effective contraceptive methods such as the IUD were adopted by the general population, to the present. Combined with the [[sexual revolution]] and the increased role of women in society and the workforce the resulting changes have profoundly affected the demographics of industrialized countries resulting in a [[sub-replacement fertility]] level.<ref name="Kaa012902">{{cite journal|author1=Dirk J. van de Kaa|title=The Idea of a Second Demographic Transition in Industrialized Countries|date=29 January 2002|url=http://websv.ipss.go.jp/webj-ad/WebJournal.files/population/2003_4/Kaa.pdf|access-date=May 6, 2016|archive-date=29 October 2020|archive-url=https://web.archive.org/web/20201029113743/http://websv.ipss.go.jp/webj-ad/WebJournal.files/population/2003_4/Kaa.pdf|url-status=dead}}</ref>

The changes, including increased numbers of women choosing to not marry or have children, increased cohabitation outside marriage, increased childbearing by single mothers, increased participation by women in higher education and professional careers, and other changes are associated with increased individualism and autonomy, particularly of women. Motivations have changed from traditional and economic ones to those of self-realization.<ref name="PNAC122314">{{cite journal|author1=Ron Lesthaeghe|title=The second demographic transition: A concise overview of its development|journal=Proceedings of the National Academy of Sciences of the United States of America|date=December 23, 2014 |volume=111|issue=51|pages=18112–18115|doi=10.1073/pnas.1420441111|pmid=25453112|pmc=4280616|bibcode=2014PNAS..11118112L|doi-access=free}}</ref>

In 2015, Nicholas Eberstadt, political economist at the [[American Enterprise Institute]] in Washington, described the Second Demographic Transition as one in which "long, stable marriages are out, and divorce or separation are in, along with serial cohabitation and increasingly contingent liaisons."<ref name="WSJ_Eberstadt_2015">{{citation |quote='They're getting divorced, and they'll do anything NOT to get custody of the kids." So reads the promotional poster, in French, for a new movie, "Papa ou Maman"|title=The Global Flight From the Family: It's not only in the West or prosperous nations—the decline in marriage and drop in birth rates is rampant, with potentially dire fallout |author=Nicholas Eberstadt |url=https://www.wsj.com/articles/nicholas-eberstadt-the-global-flight-from-the-family-1424476179|date=February 21, 2015 |access-date=February 26, 2017 |publisher=Wall Street Journal }}</ref>[[S. Philip Morgan]] thought future development orientation for SDT is Social demographers should explore a theory that is not based on stages, a theory that does not set a single line, a development path for some final stage—in the case of SDT, a hypothesis that looks like the advanced Western countries that most embrace postmodern values.

[[S. Philip Morgan]] thought future development orientation for SDT is Social demographers should explore a theory that is not based on stages, a theory that does not set a single line, a development path for some final stage—in the case of SDT, a hypothesis that looks like the advanced Western countries that most embrace postmodern values.

However, the Second Demographic Transition (SDT) theory has not proposed a single line or teleological evolution based on phases, as was the case for the theories of the First Demographic Transition (FDT). Instead, and this is strikingly in evidence in Lesthaeghe's empirical studies, major attention is being paid to historical path dependency, heterogeneity in the SDT patterns of development, forms of family and lineage organisation, economic and especially ideational developments.<ref>Johan Surkyn and Ron Lesthaeghe, 2004: Value Orientations and the Second Demographic Transition (SDT) in Northern, Western and Southern Europe- An Update. Demographic Research, Special collection, 3: 45-86. Ron Lesthaeghe, 2010: The Unfolding Story of the Second Demographic Transition. Population and Development Review, 36 (2), 211-251</ref>

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* [[Neolithic demographic transition]]

* [[Zelinsky Model|Migration transition model]]

* [[Population change]]

* [[Population pyramid]]

* [[Rate of natural increase]]