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Population aging is transforming the world in dramatic and fundamental ways. The age distributions of populations have changed and will continue to change radically, due to long-term declines in fertility rates and improvements in mortality rates (Table 93e-1). This transformation, known as the Demographic Transition, is also accompanied by an epidemiologic transition, in which noncommunicable chronic diseases are becoming the major causes of death and contributors to the burden of disease and disability. A concomitant of population aging is the change in key ratios expressing “dependency” of one form or another—the ratio of adults in the workforce to those typically out of the workforce, such as infants, children, retired “young old” (those still active but in ways other than paid work), and the oldest old. Global aging will affect economic growth, migration, patterns of work and retirement, family structures, pension and health systems, and even trade and the relative standing of nations. Both absolute numbers (the size of an age group) and ratios (the ratio of those in working ages to dependents such as the young or retired, or the ratio of children to older people) are important. The size of age groups might affect the number of hospital beds needed, whereas the ratio of children to older people could affect the relative demand for pediatricians and geriatricians.

TABLE 93e-1Selected Indicators of Population Aging, Estimates for 2009, and Projections to 2050; Selected Regions and Countries

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