Life Expectancy in the United States
Released: 2006-08-16T00:00:00

Introduction

This report considers population longevity in the United States, as measured by life expectancy. Life expectancy is the expected number of years to be lived, on average, by a particular cohort, if current mortality trends continue for the rest of that cohort's life. It most commonly refers to life expectancy at birth , the median number of years that a population born in a particular year could expect to live. For instance, based on recently released final data, life expectancy at birth in 2003 was 77.5 years. This tells us that, for those born in calendar year 2003 in the United States, 50% will die before that age; the other half will live longer.

Life expectancy is also routinely calculated for other ages. Life expectancy at age 60, for instance, refers to the additional number of years that a person who has already attained age 60 will live beyond age 60. Life expectancy at age 60 in the year 2003 was 22.2 years in the United States. A person who reached age 60 in 2003 was expected to live an additional 22.2 years, on average, and would die at age 82.2. While this report concentrates on trends and differentials in life expectancy at birth , Appendix B Table B -2 provides estimates of life expectancy at selected additional ages in 2003 (the most recent final data available).

Measures of life expectancy are published in official life tables, which are based on age-specific death rates. In the United States, data on mortality are collected and compiled through the vital statistics system by the Centers for Disease Control and Prevention (CDC)/National Center for Health Statistics (NCHS). The most recently released final data on deaths and mortality are for calendar year 2003; preliminary estimates are often released by NCHS but are generally not referred to in this report.

The concept of life expectancy , which considers the average experience for a population, is distinct from the concept of life span , which considers the upper limit of human life that could be reached by an individual. According to the U.S. Census Bureau, International Data Base, the highest attained life expectancy to date for a national population was that of Andorra in 2006, when life expectancy was 83.5 years for the total population (86.6 years for females; 80.6 years for males). The oldest authenticated female life span thus far recorded was for J. Calment of France, who died at age 122 years, 164 days, and, for a man, C. Mortensen (a Danish immigrant to the U.S.), who died at age 115 years, 252 days. There is a lively debate among researchers regarding whether the biological limits of life spans have been reached or whether future increases are probable. Life spans are not considered further in this report.

This report documents the improvements in life expectancy that have occurred, analyzing both the underlying factors that contributed to mortality reductions as well as the continuing longevity differentials by sex and race. In addition, it considers whether life expectancy will continue to increase in future years. While this report focuses on describing the demographic context of longevity change in the United States, these trends have implications for a wide range of social and economic issues that are likely to be considered by Congress. For instance, one consequence of lengthening life expectancies is that the older population's needs for careâassistance with daily tasks to allow continued community-living for high-functioning seniors, institutions for those with more severe disabilities or cognitive impairments, training of a specialized work force in geriatric careâare likely to increase, particularly for the oldest-old. There are also questions with respect to ensuring basic income support, medical care, and housing for the older population. At the same time, there is the recognition that government programs, such as Social Security and Medicare, will face financial pressures to meet the increasing needs. What program changes are required to ensure the continued viability of such programs as the number of beneficiaries increases? What will be the federal government's role in an environment of competing demands for limited resources?

Trends in the Level of Longevity Over the Past Century

As seen in Table 1 and Appendix B Table B -1 , life expectancy at birth increased dramatically over the past century in the United Statesâfrom 49.2 years (the average for 1900-1902) to 77.5 years in 2003, the most recent year for which official data have been released by the Centers for Disease Control (CDC)/National Center for Health Statistics (NCHS).

Gains in longevity were fastest in the first half of the 20 th century. These advances were largely attributed to "an enormous scientific breakthroughâthe germ theory of disease" which led to the eradication and control of numerous infectious and parasitic diseases, especially among infants and children . The new theory led to an entirely new approach to preventative medicine, practiced both by departments of public health and by individuals. Interventions included boiling bottles and milk, washing hands, protecting food from flies, isolating sick children, ventilating rooms, and improving water supply and sewage disposal. Beginning in the 1940s, the control of infectious diseases was also aided by the increasing distribution and usage of antibiotics, including penicillin and sulfa drugs.

Since mid-century, advances in life expectancy have largely been attributable to improvements in the prevention and control of the chronic diseases of adulthood . In particular, death rates from two of the three major causes of death in 1950âdiseases of the heart (i.e., coronary heart disease, hypertensive heart disease, and rheumatic heart disease) and cerebrovascular diseases (stroke)âhave fallen by approximately 60% and 70%, respectively, on an age-adjusted basis since 1950 (see Table 2 ), improvements that the CDC has characterized as "one of the most important public health achievements of the 20 th century."

The CDC attributes the declines in diseases of the heart and cerebrovascular diseases to a combination of

medical advances , including

âdiscoveries in diagnosing and treating heart disease and stroke;

âdevelopment of effective medications for treatment of hypertension and hypercholesterolemia;

âgreater numbers of specialists and health-care providers focusing on cardiovascular diseases;

âan increase in emergency medical services for heart attack and stroke; and

âan increase in coronary-care units.

changes in individually controlled behaviors , including

âdeclines in cigarette smoking;

âdecreases in mean blood pressure levels;

âan increase in persons with hypertension who have the condition treated and controlled;

âa decrease in mean blood cholesterol levels; and

âchanges in the American diet (reductions in the consumption of saturated fat and cholesterol).

Beyond medical interventions, public health measures, and individual behaviors, a number of additional factors are known to be associated with mortality decline. They are briefly mentioned here, but it is beyond the scope of this report to discuss them in detail or to disentangle them from the factors already described:

Socioeconomic status (SES) . Higher SES persons tend to be better educated, have higher incomes, and practice better individual behaviors (less smoking, healthier diets, etc.), and are more likely to have financial resources or health insurance to ensure access to medical care. Social policies . Some social policies, such as Medicare and Medicaid, are oriented to health improvements. Both programs were designed to increase access to health care for vulnerable populations, the elderly and the poor, with the ultimate goal of improving health for these groups. Other social policies, such as Social Security, affect income, and may affect health and well-being through that channel. Finally, some social policies may affect health by changing the access that people have to already-established resources. An example is the combination of civil rights legislation and improved health programs for the poor during the mid-1960s, especially through Medicaid.

A Quick Global Comparison

Life expectancy in the United States, for both men and women, is significantly higher than the global average but is only slightly higher than the average for more developed countries (see Table 3 ). Life expectancy surpasses that of the United States in a large number of countries, including but not limited to Japan, Andorra, Canada, Hong Kong, Macau S.A.R, Singapore, Sweden, Australia, Martinique, Greece, Israel, Aruba, Italy, Netherlands, Norway, France, Liechtenstein, Monaco, Spain, and more. Estimates are provided for a non-comprehensive list of selected counties in Table 3 . The United States was ranked 48 th among 227 countries and territories for both sexes.

What Will Be the Future Course of American Longevity?

The Social Security Trustees report to Congress on the actuarial status of the Trust Funds annually. The long-range projections needed for this assessment depend critically on assumptions for the future course of longevity. According to Steven Goss, chief actuary of the Social Security Administration (SSA), their future mortality assumptions are based on the recorded average annual mortality decline for the total U.S. population aged 65 and older between 1900 and 2000. He asserted that assuming future mortality improvement at nearly the same rate as for the last centuryâa little more than 0.7% annuallyâis a reasonable assumption, with a roughly equal likelihood of doing better or worse. This rate of improvement is more optimisticâabout twice as largeâas experienced during the last 18 years of the 20 th century. Goss further suggested that "matching the accomplishments of the past century will not be easy. AIDS, SARS, and antibiotic resistant microbes, along with increasing obesity and declining levels of exercise, remind us that mortality improvements will not be automatic. Gains from replacement organs and genetic engineering will be expensive, and may be difficult to provide for the population as a whole." SSA's projections of period life expectancy are shown in Table 4 .

A benefit of the statistical methods that have emerged to extrapolate historical mortality trends to the future is that they have worked well and are relatively simple and efficient. In addition to being utilized by SSA, similar approaches are also used in Canada and in the United Kingdom (UK). Canada's approach assumes that economic productivity is the overall driving factor for sustained longevity improvements, and projects a relationship between future mortality decline and future real growth in employment earnings. The UK extrapolates trends from 15 years of past data to help define base starting points and establish initial rates of mortality improvement for projections. An assumption is also made that there will be a gradual slowing of rates of improvement after the first 10 years.

Future mortality and survival are, however, difficult to predict and specialists disagree on not only the level but also the direction of future trends. James Vaupel, director of the Max Planck Institute for Demographic Research, argues that the Social Security projections are too pessimistic. He notes that SSA's forecast is that female life expectancy in the United States will gradually rise from 79.5 years today to 83.4 years in 2050. SSA's projected level of life expectancy in 2050, half-a-century from today, is less than current life expectancy in Japan and France, and is 13 to 14 years less than likely Japanese and French female life expectancy in 2050. Vaupel further suggests that it is unrealistic for SSA to assume that the United States will be unable to match the level of life expectancy in half-a-century that is already attained in other countries today.

A number of articles suggested that current models may be too pessimistic in their assumptions about mortality and survival probabilities (i.e., Americans may live longer than currently projected). Two of these studies showed that there has been a tendency for international life expectancy to rise linearly by more than two years per decade over the past 40 years or the last 160 years, a more rapid pace than suggested by current models. Also, useful analyses of the contributions of smoking behavior to mortality trends in the United States suggests that slow female gains in life expectancy over the past few decades may be temporary, and that the pace may pick up fairly soon.

Technological advances also have the potential to expand life. The National Institute on Aging supports extensive analyses of genetic contributions to longevity in diverse species, as well as on the diseases and conditions that are responsible for premature death.

Differentials in Life Expectancy

Sex Differentials

Life expectancy worldwide is generally higher for females than for their male counterparts. The United States is no exception; female life expectancy exceeded that of males in all years of the past century (see Figure 1 ).

The average girl born at the turn of the 20 th century in the United States could expect to live 50.7 years, roughly three years more than an American boy born at the same time. From 1900 to 1975, the difference in life expectancy increased from 2.0 years to 7.8 years, with females continuing to have the longevity advantage. In the absence of war, such large differences between the sexes in life expectancyâwhich were also being recorded in other developed countriesâare a relatively recent phenomenon in demographic history. For the United States, NCHS attributed the increasing gap during these years to increases in male mortality due to ischemic heart disease and lung cancer, which were largely the result of men's early and widespread adoption of cigarette smoking. In the mid- to late 1970s, the average gap in life expectancy approximated the average gap seen in developed countries todayâroughly seven years. The gap has been recorded as great as 13 years, as seen in parts of the former Soviet Union in recent years as a result of unusually high levels of current adult male mortality.

Since 1979, the "female advantage" in life expectancy between the sexes in the United States has narrowed from 7.8 to 5.3 years, reflecting proportionately greater increases in lung cancer mortality for women than for men and proportionately larger decreases in heart disease mortality among men. The average girl born in 2003 in the United States could expect to live 80.1 years compared to 74.8 years for a boy born in the same year.

A now dated, but still informative, study evaluated the contributions of various causes of death to the size of sex differentials in life expectancy in developed countries for the early 1980s. Diseases of the circulatory system were found to account for nearly 40% of the mean sex differential in life expectancy; neoplasms (cancer) for 18%, accidents, suicide, and violence for 19%, and diseases of the respiratory system for nearly 10%.

In general, why is life expectancy longer for women? The answer, which is still being investigated, involves the complicated interplay of a host of biological, social, and behavioral conditions. In addition, it differs according to age and to the underlying disease and mortality profiles for men and women. At birth, boys have a clear advantage. In the United States, 104.9 boys were born for every 100.0 girls in 2003. But, male mortality exceeds that of females in every age group and for most major causes of death, beginning in infancy and continuing through the oldest-old age groups. One researcher has suggested that the male advantage at birth is moderated by higher male mortality to "ensure that the number of men and women will be about the same at reproductive age."

Biological Factors

It has long been argued that hormones play a role in longevity. As described by Desjardins, the female hormone estrogen helps to eliminate "bad" cholesterol (LDL) and thus may offer some protection against heart disease. In contrast, some say, testosterone, found in greater amounts in males, may make men more likely to engage in violence and risk-taking behavior, especially if reinforced by cultural influences. Women may also gain an additional biological advantage because of their two X chromosomes. If a gene mutation occurs on one X, a woman's second X chromosome may be able to compensate. In comparison, genes on men's sole X chromosome may be expressed, even if they are deleterious without compensation.

Stindl, however, argues that these classic biological explanations do not withstand critical analysis. He offered an alternative hypothesis that has not yet been subject to long-term scientific scrutiny. He asserts that a strong positive correlation has been reported between sexual size dimorphism (SSD) and male-based mortality, with men being the larger/taller sex globally. A larger body requires more cell doublings, especially due to the ongoing regeneration of tissues over a lifetime. Accordingly, the replicative history of male cells might be longer than that of female cells, resulting in the exhaustion of the regeneration potential and the early onset of age-associated diseases predominantly in males. The underlying mechanism is the gradual erosion of chromosome ends (telomeres). Two recent studies confirm that men do have shorter telomeres than women at the same ages. Numerous studies also demonstrate links between chronic stress and indices of poor health, including risk factors for cardiovascular disease and poorer immune function.

Behavioral and Social Differences

Many researchers believe that behavioral and social factors also contribute significantly to the sex differentials observed between men and women. Women's social status and life conditions (such as the hardships associated with childbirth) may have nullified American women's biological advantage at the beginning of the 20 th century but are no longer major factors in gender differentials in life expectancy in the United States, though these explanations are still relevant in a number of other countries. Higher male mortality rates have been attributed to greater male exposure to specific risk factors, such as alcohol consumption and occupational hazards. Life expectancy in Russia, for instance, fell by 6.3 years for Russian men during the period 1990 to 1995âa level of decline that was unprecedented both in Russia and in other industrialized countries. In investigating the cause of the sudden drop, a team of researchers from the London School of Economics and the Russian Academy of Sciences observed that excessive alcohol consumption contributed both directly and indirectly to the marked increases in deaths from fatal events (e.g. accidents, injuries, suicides, poisonings) and in deaths from cardiovascular disease.

The most cited behavioral contributor to higher male mortality rates in the United Statesâand the subject of considerable research interestâhas been the greater male exposure to cigarette smoking. Smoking patterns are an obvious place to look for an explanation of sex mortality differences because the health risks are high and long-lasting; large fractions of the population have engaged in the habit; and smoking patterns differ between the sexes. More specifically, women's uptake of smoking lagged behind that of men. In the 1970s, when the sex differential in mortality was increasing, cigarette smoking was implicated. Now, as the sex differential is narrowing, a new body of research is evaluating the role of cigarette smoking in explaining the trend. Pampel, for instance, documented that the rate of decline in female mortality in the United States has slowed since 1980 or so, while that of males has returned to its earlier trend of relatively rapid improvementâthus resulting in a narrowing life expectancy differential by gender. He concludes that smoking behavior lies behind the changing pace of mortality decline not only in the United States, but also in 20 other industrial nations. Extending Pampel's analysis, Lee showed that the rate of decline for deaths not associated with smoking was actually faster for women (than men) while death rates associated with smoking actually increased for women while decreasing for men. Preston and Wang demonstrate that changes in sex mortality differences in the United States have been structured on a cohort rather than a period basis, and that the cohort imprint is closely related to histories of cigarette smoking. Allowance for the smoking histories of cohorts significantly affects the assessment of mortality trends: national mortality levels would have declined more rapidly in the absence of smoking, and they are likely to decline more rapidly in the future as smoking recedes.

Race Differentials54

Life expectancy at birth for whites significantly exceeded that for blacks at the turn of the 20 th century (see Figure 2 and Appendix B Table B -1 ). At that time, the expected longevity of a white newborn girl exceeded that of a black newborn girl by about 16.0 years (with longevity measured at 51.1 years vs. 35.0 years, respectively). For newborn boys, the white advantage was 15.7 years (48.2 years vs. 32.5 years).

The gap between whites and blacks in average longevity declined significantly over the past century ( Figure 3 ). For females , the improving situation for black women relative to their white counterparts was dramatic and mostly consistent throughout the century. From the height of the differential in 1904âwhen white women survived, on average, 17.9 years longer than black womenâthe gap fell to 4.4 years in 2003.

A significant reduction in the life expectancy gap between American white and black men was also observed over the 20 th century. From its height of 17.8 years in 1904, the differential had fallen to 6.3 years in 2003. The improvement was most rapid in the first six decades of the past century. Since the mid-1950s, however, improvements for males have stagnated in the range of roughly 6.0 to 8.5 years. While the male gap has been falling over the past decade, this trend obscures the fact that the differential had already been at or near this level for most of the mid-1950s to mid-1960s. The gap in 1961 was narrower than that observed todayâat that time, the gap between white and black men was 5.8 years (as compared to 6.3 now). Factors that contribute to the differential are discussed in later sections of this report.

In summary, mortality rates in the United States have declined dramatically over the past century. Black persons, however, still live, on average, 5.3 fewer years than their white counterparts. In 2003, the most recent year for which we have official data, the highest life expectancy was observed for white females, who will live, on average, 80.5 years. The values for black females and white males are quite similar to each otherâ76.1 years and 75.3 years, with black females having the slight advantage. Of the four race-sex groups considered, black males have the shortest average longevityâ69.0 years. Within-sex groupings, whites have the advantage for both females and males.

What accounts for the higher mortality, and subsequent lower life expectancy for blacks, and especially for black men in the United States? This has been a subject of research by medical and social scientists for at least a century, and the issue stands at the heart of the current public health agenda in the United States. One of the two primary goals of Healthy People 2010 is to eliminate health disparities.

Mortality from most, but not all, causes of death are higher for blacks, and a number of researchers have investigated which specific diseases contribute most to life expectancy differences between the races. Wong and colleagues, for instance, recently calculated potential years of life lost related to specific causes of deaths for blacks and whites in the United States ( Table 5 ).

As seen in Table 5 , when considering the major categories of disease, deaths from cardiovascular disease contributed most to the racial disparity in mortality from any cause (34.0%), followed by infection (21.1%), and trauma (10.7%).

When looking at specific diseases, the leading sources of the disparity were largely preventable causes of premature deathâhypertension (which contributed 15.0% to the disparity), followed by HIV disease (11.2%), diabetes (8.5%), and homicide (8.5%). Note that blacks had a lower mortality risk from respiratory diseases (lung disease), suicide, and certain types of cancer (breast, colon, uterus or ovary, bladder or kidney, and leukemia or lymphoma; figures are in the original source but are not shown in table). These results are consistent with findings from other studies, and are said to show that "most of the influential diseases are ones in which the rates vary based on avoidable risks such as smoking, exposure to HIV, and obesity. [And,] this adds to the credibility of public-health interventions aimed at reducing the exposure to these risk factors." The results may also offer hope for the elimination of racial disparities in health.

Beyond describing gross health disparities, scientific inquiry has shifted to explaining the underlying factors that account for these differences in health outcomes. Understanding these underlying causes requires disentangling the complex web of factors connecting the nexus among race, socioeconomic status, behavioral factors, and health. Some have argued that, if pertinent differences between whites and blacks in their underlying social, demographic, familial, and economic circumstances were eliminated, racial differences in mortality would be significantly reduced. ,

Socioeconomic arguments cite the consequences of lifelong poverty. Relevant factors include both early-life differences, such as birth weight and childhood nutrition, and mid-life variables (such as access to employer-provided health insurance, the strain of physically demanding work, and exposure to a broad range of toxins, both behavioral (e.g., smoking) and environmental (e.g., workplace exposures). Over the life cycle, these factors combine to increase the demand for health care, while potentially limiting consumption of necessary health services. In late life, these factors may affect the age of onset of both morbidity and disability, the severity of symptoms, and ultimately the age at, and cause of death.

In addition, Martin and Soldo note that there are differences between racial groups in norms regarding not only lifestyle and self-care behaviors, but also in access to health care providers and treatment compliance. Moreover, the experience of racial discrimination may have adverse psychological and physiological effects, in addition to limiting the quantity and quality of health care received. Some of these factors that contribute to the racial gap in life expectancy will be discussed briefly in the following paragraphs.

Economic and Social Factors

In general, as income increases, mortality decreases, because high income provides access to high-quality health care, diet, housing, and health insurance. Black households had the lowest median income in the United States in 2003. Their median money income was about $30,000, which was 62% of the median for non-Hispanic White households (about $48,000). Poverty rates among African Americans are persistently higher than those of non-Hispanic whites. In 2003, 24.4% of blacks were poor, compared to 8.2% of non-Hispanic whites.

Recent research also highlights the enduring effects of education. Increased education appears to lower the risks for some chronic diseasesâmost notably, coronary heart disease (which is the leading cause of death in the United States)âwhile retarding the pace of disease progression for other conditions. In 2003, the proportion of both blacks and non-Hispanic whites who had a high school diploma (of persons in the population aged 25 and over) reached record highs but at different levels for the two racial groupsâ80% and 89%, respectively. The gap in educational attainment is also apparent among recipients of bachelor's degreesâ30% of non-Hispanic whites aged 25 and older had attained a four-year college degree compared to 17% of blacks.

Marriage is also a socioeconomic determinant that is related to health outcomes. Married people consistently exhibit lower levels of mortality than those who are not married. Marriage acts to select healthy individuals, but it also enhances social integration and encourages healthful behaviors. Race differences in marital and cohabitational stability are substantial, and may be increasing over time. About 91 percent of white women born in the 1950s are estimated to marry at some time in their lives, compared with 75% of black women. Black married couples are more likely to break up than white married couples, and black divorcees are less likely to remarry than white divorcees. The degree of attachment to marriage among black Americans is similar to that of white Americans as measured by attitudes toward marriage. One explanation offered by some researchers for the lower proportion of time spent in marriage among black Americans is the idea of a "marriage squeeze," in which the "marriageable pool" of black men is low due to high rates of joblessness, incarceration, and mortality. Employed men are more likely than unemployed men to marry.

Behavioral Risk Factors

Prolific research over the past two decades has confirmed the link between certain diseases and health outcomes and various health-damaging (such as smoking, alcohol abuse) and health-promoting (exercise, low-fat diet) behaviors. And, some researchers have explored the extent to which health-damaging and health-promoting behaviors explain black-white differences in health status. Berkman and Mullen, for instance, found that, despite greater apparent concern on the part of blacks than whites about their health, blacks do not consistently adopt more beneficial behaviors than whites. Older blacks engage in less physical activity and are more likely to be obese (especially women), but they are less likely to consume alcohol than whites. Racial differences in smoking patterns are complex, with older blacks less likely to have smoked but, if they have, less likely to have quit. Lack of exercise and obesity are associated with hypertension and diabetes, both of which have been reported to be twice as common among blacks than among whites.

Access to Health Care

The United States is the only developed country in the world that does not have national health coverage, and significant numbers of Americans, and especially African Americans, do not have sufficient health care coverage. More specifically, 21.0% of blacks under age 65 and 12.9% of whites of the same age lacked private health insurance in 2003.

Beyond health insurance, Chandra and Skinner argue that there is differential access to health services in the United States, especially because of geographic variation in treatment and outcome patterns. Minorities tend to seek care from different hospitals and from different physicians than non-Hispanic whites, in large part a reflection of the general spatial distribution of the United States population with concentrations of minorities in certain hospital referral regions.

Genetic Factors

Some research suggests that there are race-related genetic factors both for predisposing conditions, such as hypertension and diabetes mellitus, and for life-threatening conditions, such as aplastic anemia. As recently noted by the National Research Council, however, "Probably no aspect of the debate about the causes of racial differences in health is potentially more sensitive than the discussion about the extent to which genetic factors are in any way responsible. There are numerous historical examples of scientific mischief in the support of racism." Those in favor of using race assert that there is a useful degree of association between genetic differences and racial classifications, so that the use of race as a research variable is warranted. Opponents, however, argue that bundling the population into four or five categories based on skin color or other traits is not a useful way to summarize genetic variation when we know that there are at least 15 million genetic polymorphisms in humans, of which an unknown number underlie variation in (normal and) disease traits.

Research in this area is still in its infancy and tends to reflect two ways that genes may be relevant to the study of health differentials. First , there are a small number of conditions with single-gene disorders in populations that have descended from a relatively small number of people and that remain endogamous (an example is Tay-Sachs Disease among Ashkenazi Jews). Second , genes may be relevant to the study of health differentials through environmental factors, which may vary by racial or ethnic group, and which might interact with genotype to produce different outcomes for different groups.

Conclusion

One of the most important public health achievements of the 20 th century in the United States was the dramatic and widespread increase in life expectancy that occurred over the past century in the United Statesâfirst as a result of the control of the infectious and parasitic diseases that had plagued mostly infants and children in the early part of the century, and later because of medical advances that led to large decreases in adult mortality, especially from two of the most prevalent causes of deathâcardiovascular diseases and cerebrovascular diseases.

A consequence of the improved survival, coupled with declining fertility rates, is that the United States is in the midst of a profound demographic change: rapid population aging, a phenomenon that is replacing the earlier "young" age-sex structure with that of an older population. Hastened by the retirement of the "Baby Boom" generation (the cohort born between 1946 and 1964), the inexorable demographic momentum will have important implications for a large number of essential economic and social domains, including work, retirement, and pensions, wealth and income security, and the health and well-being of the aging population.

Whether the life expectancy improvements will continue is the subject of intense debate. The Social Security Administration (SSA) assumes that the rate of future mortality improvements will be nearly the same as for the last centuryâa little more than 0.7% annuallyâwhile asserting that it may be difficult to match the accomplishments of the past century, especially in light of increasing obesity, declining levels of exercise, and the introduction of new scourges, such as AIDS, SARS, antibiotic resistant microbes. Some demographers, on the other hand, feel that such projections are pessimistic, and argue, based on historical trends and evidence from other developed countries, that American survival will be longer than that projected by SSA. The outcome of the debate has important implications for determining the number of future beneficiaries and ultimately the financial soundness of the Social Security and the Medicare programs.

This report also highlights the continuing differentials in life expectancy by race and sex in the United States, with black males continuing to be the most disadvantaged group on this measure. Life expectancy at birth in 2003 for black males measured 69.0 years, falling short of the comparable figure for white males by 6.3 years. The gap between black and white men has remained relatively stagnant since the mid-1950s.

The sources of the racial disparities in life expectancy are complex and require disentangling the complex web of factors connecting the nexus among race, socioeconomic status, behavioral factors, and health. Differences exist on a wide variety of important variables including lifetime income and wealth, marriage patterns, birth weight and childhood nutrition, access to employer-provided health insurance, the strain of physically demanding work, exposure to toxins, risky behaviors (such as smoking, high saturated diet), adherence to preventative health measures (such as maintaining a healthy weight, exercise), and access to and quality of health care. In addition, the experience of racial discrimination may have adverse psychological and physiological effects, in addition to limiting the quantity and quality of health care received.

Recent research, however, that shows that the leading specific diseases that are the main sources of the racial disparity in life expectancy are largely preventable causes of premature death offers hope that public-health interventions can reduce the racial disparities. Specifically, the leading causes of the racial disparity were hypertension (which contributed 15.0% to the disparity), followed by HIV disease (11.2%), diabetes (8.5%), and homicide (8.5%) in a recent analysis.

Appendix A. Glossary of Terms

Appendix B. Detailed Life Expectancy Tables