Editing Demographic transition (section)

===Stage two===
[[File:Population curve.svg|thumb|upright=1.7|right|World population 10,000 BC-2017 AD]]
This stage leads to a fall in death rates and an increase in population.<ref>{{Cite web|url=http://www.bbc.co.uk/schools/gcsebitesize/geography/population/popchangestructurerev5.shtml|archiveurl=https://web.archive.org/web/20071023172810/http://www.bbc.co.uk/schools/gcsebitesize/geography/population/popchangestructurerev5.shtml|url-status=dead|title=BBC bitesize|archivedate=October 23, 2007}}</ref> The changes leading to this stage in Europe were initiated in the [[British Agricultural Revolution|Agricultural Revolution]] of the eighteenth century and were initially quite slow. In the twentieth century, the falls in death rates in developing countries tended to be substantially faster. Countries in this stage include [[Yemen]], [[Afghanistan]], and [[Iraq]] and much of [[Sub-Saharan Africa]] (but this does not include [[South Africa]], [[Botswana]], [[Eswatini]], [[Lesotho]], [[Namibia]], [[Gabon]] and [[Ghana]], which have begun to move into stage 3).<ref name=Caldwell10>Caldwell (2006), Chapter 10</ref>{{update inline|date=January 2020}}

The decline in the death rate is due initially to two factors:
* First, improvements in the food supply brought about by higher yields in agricultural practices and better transportation reduce death due to starvation and lack of water. Agricultural improvements included [[crop rotation]], [[selective breeding]], and [[seed drill]] technology.
* Second, significant improvements in public health reduce mortality, particularly in childhood. These are not so much medical breakthroughs (Europe passed through stage two before the advances of the mid-twentieth century, although there was significant medical progress in the nineteenth century, such as the development of [[vaccination]]) as they are improvements in water supply, [[sanitary sewer|sewerage]], food handling, and general personal [[hygiene]] following from growing scientific knowledge of the causes of disease and the improved education and social status of mothers.

A consequence of the decline in mortality in Stage Two is an increasingly rapid growth in population growth (a.k.a. "[[population explosion]]") as the gap between deaths and births grows wider and wider. Note that this growth is not due to an increase in fertility (or birth rates) but to a decline in deaths. This change in population occurred in north-western Europe during the nineteenth century due to the [[Industrial Revolution]]. During the second half of the twentieth century less-developed countries entered Stage Two, creating the worldwide rapid growth of number of living people that has demographers concerned today. In this stage of DT, countries are vulnerable to become [[Failed States Index|failed states]] in the absence of progressive governments.

[[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, 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.