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Introduction

Samuel H. Preston and Linda G. Martin

The populations of North America, Latin America, Europe, and Asia are rapidly growing older, primarily as a result of fertility and mortality levels that are below those of the recent past. Even if fertility and mortality levels cease declining, a great deal more aging is in prospect for these regions as their age structures approach the equilibrium that is consistent with their new levels of fertility and mortality.

Table 1-1 presents information on the size, growth, and proportionate representation of the population aged 65 and over, in major regions of the world, from 1955 to 2025. By 2025 the United Nations anticipates that there will be 822 million people in the world aged 65 and over, a number that exceeds the present combined populations of Europe and North America. The elderly population will have grown by a factor of 2.5 between 1990 and 2025. This growth is faster than that of the total population, so that the proportion of the elderly in the world's population will increase from 6.2 to 9.7 percent.

While the growth rate of the total population is expected to decline between 1955-1990 and 1990-2025, the growth rate of the elderly component is expected to accelerate. Most of the growth will occur in developing regions. As recently as 1975, a majority of the world's elderly lived in economically developed regions; by 2025 only 31 percent will do so. How rapidly the aging process will accelerate over the next several decades is indicated by the fact that the proportion of elderly persons in the world's population grew by only 1 percentage point between 1955 and 1990, whereas



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Demography of Aging 1 Introduction Samuel H. Preston and Linda G. Martin The populations of North America, Latin America, Europe, and Asia are rapidly growing older, primarily as a result of fertility and mortality levels that are below those of the recent past. Even if fertility and mortality levels cease declining, a great deal more aging is in prospect for these regions as their age structures approach the equilibrium that is consistent with their new levels of fertility and mortality. Table 1-1 presents information on the size, growth, and proportionate representation of the population aged 65 and over, in major regions of the world, from 1955 to 2025. By 2025 the United Nations anticipates that there will be 822 million people in the world aged 65 and over, a number that exceeds the present combined populations of Europe and North America. The elderly population will have grown by a factor of 2.5 between 1990 and 2025. This growth is faster than that of the total population, so that the proportion of the elderly in the world's population will increase from 6.2 to 9.7 percent. While the growth rate of the total population is expected to decline between 1955-1990 and 1990-2025, the growth rate of the elderly component is expected to accelerate. Most of the growth will occur in developing regions. As recently as 1975, a majority of the world's elderly lived in economically developed regions; by 2025 only 31 percent will do so. How rapidly the aging process will accelerate over the next several decades is indicated by the fact that the proportion of elderly persons in the world's population grew by only 1 percentage point between 1955 and 1990, whereas

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Demography of Aging TABLE 1-1 Growth of the Population Aged 65 and over by Major World Region, 1955-2025   Number of Persons Aged 65 and Over in Millions (percentage) Factor of Growth of the Population Aged 65+ Region 1955 1975 1990 2005 2025 1955-1990 1990-2025 World 143 232 328 475 822 2.29 2.51   (5.2) (5.7) (6.2) (7.1) (9.7)      More Developed Regions 72 118 145 186 256 2.01 1.76   (8.1) (5.7) (6.2) (7.1) (9.7)      Less Developed Regions 71 114 183 289 566 2.58 3.09   (3.8) (3.8) (4.5) (5.4) (8.0)      Africa 7 12 19 31 63 2.71 3.32   (3.0) (3.0) (3.0) (3.2) (4.0)      Asia 62 96 155 249 470 2.50 3.03   (4.1) (4.1) (5.0) (6.3) (9.6)      Latin America 7 13 21 33 65 3.00 3.10   (3.6) (4.1) (4.8) (8.6) (9.2)      Europe 38 59 68 82 105 1.79 1.54   (9.2) (12.3) (13.4) (15.4) (19.4)      North America 16 25 35 39 67 2.19 1.91   (8.7) (10.3) (12.5) (12.3) (18.5)      NOTE: For projections in 2005 and 2025, the medium variant is used. SOURCE: Data from United Nations (1993).

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Demography of Aging it will grow by 3.5 percentage points over the next 35 years, including a 6.3-point increase in developed regions. Population aging will be one of the most important social phenomena of the next half century. It is important because eligibility for most major social transfer programs are strongly tied to age and so are affected by changes in age population structures. It is important because people of different ages have different capabilities, interests, needs, and intentions, so that shifts in age structure gradually change the points of emphasis on the social landscape and the focus of public attention. And it is important because changes in the aggregate age structure are mirrored within nearly all social institutions, from firms to families. How these institutions accommodate themselves to impending changes in population age structures will have a significant effect on the quality of life in the twenty-first century. In view of the rapidity and significance of these changes, an increasing number of demographers and other social scientists have begun to examine the implications of population aging for a variety of social and economic processes. A field loosely called ''the demography of aging" has emerged in the past decade. The term has become a rather capacious umbrella for a variety of studies addressed to the causes and consequences of population aging. These studies have in common an empirical emphasis, typically using survey or vital statistics data. They also exhibit one or more of the following features: an orientation towards intergenerational relations and exchanges, especially within the family; a concern with cohorts and the process by which cohorts carry forward their histories into new age categories and replace cohorts with different histories; and a focus on the characteristics and behaviors of older people themselves, especially in the critical areas of economics and health. This volume includes nine chapters that map out the major themes in the demography of aging. The authors, people at the forefront of research in a particular field, provide a state-of- the-art assessment of research and identify the major gaps in data, theory, and research design. Although the focus is on the United States, each chapter also includes some attention to international developments. In Chapter 2 Ronald Lee develops a demographic accounting framework for evaluating systems of transfer among people in different age groups. He first describes how mortality and fertility levels combine to affect life-cycles and population characteristics. He then combines these demographic structures with age patterns of consumption, production, and social trans-

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Demography of Aging fers to show how the balance of flows is influenced by demographic features. The chapter makes rigorous the notion that, if taxes are paid at an average age that is below that at which benefits are received, as is currently the case in the United States, then a population that is on average older must have a more adverse balance of lifetime transfers than a younger population. The consequences are surprisingly large. For example, a 1-year gain in life expectancy at birth, under conditions of the contemporary United States, will reduce the lifetime value of consumption by 0.9 percent unless labor effort increases. The macrolevel, steady-state relations described by Lee clearly demonstrate the challenges for social policy that are posed by aging populations. They also set the stage for the microlevel analyses that occupy most of the rest of the volume. Joseph Quinn and Richard Burkhauser in Chapter 3 focus on labor force behavior of older persons. They show that, contrary to the increased work effort needed to avert a decline in life-cycle consumption in an aging population, older workers have been retiring from the labor force at younger ages. The authors provide a comprehensive, largely chronological review of an increasingly sophisticated literature about work incentives for older persons. Quinn and Burkhauser describe the efforts that researchers have made to characterize those incentives, an effort that necessarily relies on a variety of data sources that extend beyond household surveys. They also describe the evolution of models toward framing research questions in the same sequential manner in which individual workers face retirement questions. The impressive research base that already exists allows the authors to speculate about the future of labor force activity at older ages. Most of the impending changes in incentives—the reduction of pension coverage for American workers, the gradual replacement of defined benefit plans with defined contribution plans, and the changes in Social Security entitlements—suggest a halt or reversal in the movement towards earlier retirement. The authors note, however, that the research base is very thin with respect to female workers, who constitute a large and rapidly growing percentage of the work force. The economic distinctions between older men and women are highlighted in Chapter 4. Douglas Holtz-Eakin and Timothy Smeeding investigate the economic status of older Americans and compare them with persons in other developed countries. The message is one of diversity. Not only is income more unequally distributed among older Americans than among younger Americans, it is far more unequally distributed among older Americans than among older people in other countries. Much of the income inequality in the United States is associated with gender and marital status. In comparison with people in other countries, U.S. married couples aged 65 and over are by far the most affluent. In

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Demography of Aging contrast, elderly women living alone in the United States are very poor by international standards. The wider variance in income for older Americans means that, even though their median income is not unusually low relative to that in other countries, they have the highest level of poverty. The authors note that, although the data base for making these assessments of income is relatively firm, the same cannot be said for measures of wealth or intergenerational transfers of resources. Better measures of wealth would also improve income comparisons: for example, 57 percent of older single women in poverty are homeowners, and imputation for the value of those homes would reclassify a large fraction of them out of poverty. Family relationships are important not only for economic status but for virtually every feature of life. Chapter 5 by Douglas Wolf reviews research that investigates the extent of kinship ties among older people and the degree of residential proximity among kin, including residence in the same household. The emphasis is on ties between older persons and their children. Wolf notes that there is not a one-to-one correspondence between levels of fertility and mortality and the frequency of kinship ties: patterns of correlation within generations (i.e., in the form of parity-specific fertility rates) or across generations (i.e., intergenerational correlations in fertility or mortality) create far more complex patterns of kinship ties. Family dissolution and reformulation also contribute to greater complexity. After kinship patterns are mapped out, an important research question is clear: Who chooses to live with whom? Identifying the factors affecting the likelihood of coresidence has proven very difficult because coresidence is a joint decision across many potential alternatives for many potential coresidents. Although a fair amount is known about the characteristics of older persons that increase the likelihood of residing with a child—for example, health impairments and low income—much less is known about how the characteristics of offspring affect the choice. These same questions arise in Chapter 6 by Beth Soldo and Vicki Freedman. They are concerned with understanding the factors that influence the type of care received by older Americans who are disabled in some fashion. These people constitute about 24 percent of the population aged 65 and over. The possible sources of care are spouses and offspring (thus raising the same issues of research design as in the previous chapter by Wolf), friends, unpaid volunteers, paid caregivers, and public and private institutions. The possible sources of financial support for acquiring such care are oneself, one's family, state subsidies, and donations in kind by caregivers. This complex array of possibilities has proven daunting to researchers, and the chapter by Soldo and Freedman consists of more citations of inadequacy than of triumph in the literature. They have put their fingers on a very weak spot in research on the demography of aging, and one that needs

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Demography of Aging immediate attention in view of potential changes in U.S. social policy regarding the public provision of care. Changes in the incidence and case-fatality rates of major diseases jointly determine (along with fertility levels) the rate of population aging. These issues, subsumed under the title of medical demography, are the subject of Chapter 7 by Kenneth Manton and Eric Stallard. Disabled people have suffered some disease or injury that has not proven fatal. A reduced incidence of disease or injury will reduce the prevalence of disability, whereas reduced death rates for persons with a particular condition will raise the prevalence. Manton and Stallard outline a framework for analyzing the relationships among individual health-related behaviors, genetic predispositions, disease incidence and fatality, population aging, and levels of mortality and morbidity. Although this agenda is extremely ambitious, they present illustrations of how models that are biologically less complex can prove misleading. Especially provocative is their presentation and interpretation of evidence that rates of disability have recently declined at older ages in the United States. Because of the high costs of caring for people with health impairments, models that demonstrate the potential effects of various health policies and that accurately project changes in disability rates can be extremely valuable, even when their complexity prevents easy comprehension. Samuel Preston and Paul Taubman in Chapter 8 focus on the class distribution, rather than the level, of mortality and morbidity. Using educational attainment as their basic measure of social class, they show that adult mortality differentials widened between 1960 and the late 1970s, although there is some disagreement among data sources for the end of the period. Differentials among men exceed those among women, in part because of the countervailing pattern of breast cancer among the latter. For both sexes, the magnitude of class differences appears comparable to those in European countries. Class differences in mortality are not readily attributable to such standard biomedical risk factors as blood pressure and smoking; the possibility that social-psychological factors, including social relations, play an important role deserves more attention than it has received. Most of the mortality difference between blacks and whites appears attributable to the adverse distribution of blacks on socioeconomic variables. The evidence that mortality differentials at older ages widened during the period when Medicare was introduced suggests that access to health care may not play a dominant role among the determinants of mortality levels. In Chapter 9 Frank Bean, George Myers, Jacqueline Angel, and Omer Galle also disaggregate the older population, examining its geographic concentration by region and size of place. They note that the greater concentration of the elderly, and especially the population aged 85 and over, in the

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Demography of Aging Northeast and Midwest raises a host of social policy issues for local governments. The authors note the dearth of studies that attempt to identify the sources of variation in rates of aging among different localities. Certainly, migration patterns of both the elderly and nonelderly play an important role. Migration among older people appears less responsive to the economic motives that are paramount among younger people. In particular, the principal motives for migration at ages 70 and over appear to be related to family proximity and diminished health. The possibility of migration obviously affects older people's opportunities with respect to caregiving, coresidence, and economic status in ways that need to be better reflected in research. Linda Martin and Kevin Kinsella in Chapter 10 revisit many of the themes of the preceding eight chapters, but they focus on research in developing countries. Apart from Africa, many of these countries are aging as rapidly as the United States, and many of the same processes are apparent. For example, age at retirement seems to be declining as incomes rise, and residence of elderly people with their children is also declining, at least in Asia, which has been the subject of the most research. As in the United States, older people with more income are more likely to be living apart from their children. However, coresidence is still the norm, and children appear to provide a higher share of income for the elderly in Asia than is or perhaps ever was the case in the West. The authors emphasize the shortage of research and research materials in developing countries. Much of what is known is the result of censuses and a limited number of one-round cross-sectional surveys. The longitudinal studies that are providing so much detail on health, labor force, and family processes in the United States are almost completely absent in developing countries. The neglect of aging research in Latin America is especially surprising in view of the rapid aging of its population and its sizable number of social scientists. The field of the demography of aging, an offspring of mixed parentage, is rapidly approaching maturity as a subdiscipline with recognizable themes and approaches. This volume provides a kind of inventory of progress to date. Whatever success it achieves is attributable to a group of authors who were unusually diligent, perceptive, and cooperative. The editors are most grateful. REFERENCE United Nations 1993 World Population Trends and Prospects: The 1992 Revision. New York: United Nations.