Editing Demographic transition (section)

==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 |archive-date=5 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" />
* In stage four, there are 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>

As with all models, this is an idealized picture of population change in these countries. The model is a generalization that applies to these countries as a group and may not accurately describe all individual cases. The extent to which it applies to less-developed societies today remains to be seen. Many countries such as [[China]], [[Brazil]] and [[Thailand]] have passed through the Demographic Transition Model (DTM) very quickly due to fast social and economic change. Some countries, particularly African countries, appear to be stalled in the second stage due to stagnant development and the effects of under-invested and under-researched tropical diseases such as malaria and [[AIDS]] to a limited extent.