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Unit 5: Human Population Dynamics // Section 8: Demographic Convergence and Human Lifespan Trends

As the graphs in this unit illustrate, nations of the world appear to be converging demographically in several ways. The gaps between developed and developing countries for major indicators such as fertility rates and life expectancies have narrowed significantly in the past half-century and are projected to become smaller in coming decades. In 1950 life expectancy in developing countries as a whole lagged that of developed countries by 25 years. That gap has decreased to 12 years and is projected to be 8 years by 2050. Some developing countries have fertility and mortality rates that are lower than those in developed nations.

This trend indicates that the demographic transition is a widespread phenomenon and that life will continue to improve for people in poor countries as fertility rates decline further—especially if their governments adopt policies that recognize changing demographic realities, as discussed in section 7. But demographic convergence is not automatic. Some countries, including many in sub-Saharan Africa, are stuck in high fertility/low-growth traps, and others have hit speed bumps on the road toward longer, healthier lives. The HIV/AIDS pandemic has dramatically reduced life expectancy across Africa (Fig. 17). Life expectancy for men in Russia fell by more than seven years during the economic crisis and political instability that followed the breakup of the Soviet Union. Wars have left lasting marks on population distribution in some countries.

Adult HIV/AIDS rates in Africa, 2000

Figure 17. Adult HIV/AIDS rates in Africa, 2000
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Source: Courtesy United States Institute for Peace,

Economist Jeffrey Sachs argues that extremely poor nations lag behind the rest of the world for several reasons. Impoverished areas such as sub-Saharan Africa, Central Asia, and the highlands of South America have climates and land resources that are poorly suited to large-scale agriculture. They also are economically and geographically isolated, and malaria is widespread in Africa.

Sachs and his colleagues estimate that if wealthy countries doubled their foreign aid spending from $80 billion to $160 billion per year, the world's poorest nations could cut poverty in half by 2015 and eliminate it by 2025. Key investments would address core environmental needs such as clean drinking water and sanitation, along with health, education, and food production (footnote 23). In sum, for very poor countries, population is just one of a set of issues that must be addressed to jump-start economic development.

Other experts contend that massive aid plans conceived by foreign experts and imposed from the top down by international agencies and wealthy donor nations have produced very poor returns and done little to reduce global poverty. Economist William Easterly writes of Sachs and other antipoverty advocates, "Poor people die not only because of the world's indifference to their poverty, but also because of ineffective efforts by those who do care." The right approach, in Easterly's view, is to focus on smaller-scale tasks (such as delivering specific drugs to control specific diseases), relying on local channels and providers to the greatest extent possible (footnote 24).

In contrast to the situation in poor nations, most people in wealthy countries are living longer, healthier lives than at any time in history. This trend raises its own issues. For example, most of the acute illnesses that killed many people a century ago, such as tuberculosis, tetanus, and poliomyelitis, have been brought under control; one major killer, smallpox, has been eliminated. Most deaths in developed countries are now caused by chronic diseases such as cancer, heart disease, stroke, and chronic lower respiratory diseases such as emphysema. Tobacco use causes more deaths in the United States each year than HIV, alcohol use, illegal drug use, motor vehicle injuries, suicides, and murders combined (footnote 25).

Many chronic diseases develop slowly, and many are linked to personal choices such as diet. This means that effective public health programs must increasingly focus on long-term prevention and reducing risky behaviors such as smoking (Fig. 18).

Warning on a pack of British cigarettes

Figure 18. Warning on a pack of British cigarettes
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Source: Courtesy Wikimedia Commons. Creative Commons Attribution ShareAlike 2.0 License.

If we bring chronic diseases under control, could humans live even longer than they do today? On average, 1 out of 10,000 people in developed countries lives beyond age 100; the longest documented human life was that of a French woman who died in 1997 at age 122. There is great scientific interest in exploring the limits of the human life span, although no agreement on a best means for extending life or how long humans could live under optimum conditions. Most scholars believe that, absent major wars or unforeseen epidemics, life expectancy will increase during this century, to at least 85 in today's wealthy industrial countries, and perhaps to as high as 100.

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