![]() In 1800, women spent about 70 percent of their adult years bearing and rearing young children, but that fraction has decreased in many parts of the world to only about 14 percent, due to lower fertility and longer life. Population aging is a direct consequence of the demographic transition, at both the global and the country level (Chesnais 1990). The length of life, which has already more than doubled, will have tripled, while births per woman will have dropped from six to two. The Changing Demographics of Global Health Population growth and aging are fueling a spectacular rise in noncommunicable diseases, such as cancers and cardiovascular diseases, in poor countries. Incorporating the demographic transition idea into statistical models, for instance, has allowed the generation of probabilistic population forecasts by the United Nations (Raftery et al. There will then be 50 times as many elderly, but only ve times as many children thus, the ratio of elders to children will have risen by a factor of ten. Since 1800, global population size has already increased by a factor of six and by 2100 will have risen by a factor of ten. This global demographic transition has brought momentous changes, reshaping the economic and demographic life cycles of individuals and restructuring populations. It has now spread to all parts of the world and is projected to be completed by 2100. The transition began around 1800 with declining mortality in Europe. ![]() ![]() ![]() During the transition, first mortality and then fertility declined, causing population growth rates first to accelerate and then to slow again, moving toward low fertility, long life and an old population. Before the start of the demographic transition, life was short, births were many, growth was slow and the population was young. In demography, demographic transition is a phenomenon and theory which refers to the historical shift from high birth rates and high death rates in societies with minimal technology, education (especially of women) and economic development, to low birth rates and low death rates in societies with advanced technology, education and economic devel. ![]()
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