Life Expectancy

September 15, 2011

The mortality experience of a population can be summed up by the measure of life expectancy, which is the average age at death for a hypothetical group of people born in a particular year and being subjected to the risks of death experienced by people of all ages in that year. It is the average number of years to be lived either from birth or from some other specific age. Thus, the age to which the average person in a population will live is the number behind the concept of life expectancy. Life expectancy has two important applications to issues surrounding the broader topic of women’s health. First, life expectancy is sex differentiated; that is, there is a well-established difference in longevity between the sexes. Simply stated, women live longer than men: the mortality of men is greater than that of women at every age of life thereby creating a resulting advantage in life expectancy for women over men at every age. Even taking into account changeable, nongenetic behavioral and lifestyle practices such as exercise, smoking, engaging in risky behavior, and the use of health resources, there still remains a persistent biological basis for this sex difference in longevity. This increased longevity can impact and influence many diverse aspects associated with women’s health ranging from insurance rates to social security benefits to late-life migration decisions.

Second, life expectancy can be a barometer of the overall standard of living of a particular place on the surface of the Earth. For instance, since the 1950s, much of the developing world has seen sharp improvements in life expectancy due to improved nutrition, public health, and medical care, all of which have the effect of reducing the level of infant mortality and also reducing the risks associated with childbirth, which, in the past, might otherwise have endangered the health and welfare of the mother. However, life expectancy for women in sub-Saharan Africa (as just one example) is still considerably lower than that of women in the United States, Europe, or other industrialized nations. This important fact says much regarding not only the state of living conditions in sub-Saharan Africa but also about the status of women in this region. The rapid rise in heterosexual AIDS and the higher fertility rates found in the area influence the life expectancy of African women. They are indicative of cultural and societal conditions that keep women in subservient positions in relation to their male counterparts. The higher fertility rates experienced by women in less developed countries contribute to lower life expectancy: repeated pregnancies and childbirth increase the probability of dying of complications related to them. The difficulties associated with obtaining even low levels of educational attainment keep female illiteracy high, especially in hard-to-reach rural areas, thus depriving women of access to potentially lifesaving knowledge regarding contraception and other important women’s health (and women’s rights) issues.

For the world as a whole, average life expectancy has risen from about 30 years in 1900 to around 68 (for females) in 2000. The great variation in female life expectancy from nation to nation (from a low of 40 in the Central African Republic to a high of 83 in Japan) can be directly related to the level of economic development, which, in turn, affects everything from health care to literacy levels. Life expectancy is generally derived from what are known as life tables, which represent a set of tabular calculations showing the probability of surviving from one age to any subsequent age, according to the age-specific death rates prevailing at a particular time and place.

The concept of life expectancy can be explained by reference to women born in the United States. The expectation of life at birth for females born in the United States in 1998 was 79.5 years. This does not mean that the average age of death in 1998 for females was 79.5, because the life table calculations are based on a hypothetical population since it is not possible to follow people for their entire lives to calculate the pattern of dying. The life table starts with a hypothetical group of 100,000 babies born in a specific year and then subjects those babies to the probabilities of death implied by the death rates that prevailed in that year that the babies were born. Thus, if all the females born in the United States in 1998 experienced the risks of dying throughout their lives as reflected in death rates in the year they were born, then their average age at death would be 79.5. Some might die young and others might live past 100 but the average age at death for the entire population of females born in 1998 would be 79.5 years if the death rates remained unchanged over the entire lifetime of babies born in that year. In fact, it is very likely that the average age at death will be higher, since there almost certainly will be improvements in health and mortality as those babies born in 1998 mature through time.

Of course, not all females have the same risk of dying and, in addition to the sex differential discussed above, differentials in occupation, status, and role can contribute to the life expectancy differential between male and female and among female populations in different areas of the world. As stated above, there seems to be an inherent genetic biological component that contributes to the longer life expectancies found in female populations. This goes hand in hand with the fact that the risk of death appears to be greater for males at all ages, even among fetal deaths. Among adults, males tend to be employed in more hazardous occupations; military deaths, for example, are primarily male. Males are believed to be under greater stress although this is changing in developed countries as females move into more stressful occupations. Males tend to smoke and drink more. Males drive more and are more often murdered. These are all factors that raise male mortality rates thereby lowering male life expectancy. At the same time, women in different societies may also benefit differentially because fewer childbirths increase the probability of living longer while more childbirths have the opposite effect. Pregnancy puts women at risk and that risk is higher in developing nations. Marital status is also important in this respect: married people live longer than unmarried people and, as women in developed countries tend to marry later in life, thus delaying childbirth, overall fertility rates decrease as do the risks associated with childbirth. The social status of women is also related to life expectancy although this relationship will vary according to the different types of political, cultural, and economic systems. In countries where women are especially affected by a patriarchal male culture (especially South Asian countries such as Bangladesh), the life expectancy differential is almost eliminated. Women who cannot access education (or who are prohibited from doing so) are at a severe disadvantage in making lifestyle alterations that may lead to increased life expectancies.

Differences in life expectancy from society to society tend to be due to social status inequalities. As social status and prestige increase (as evidenced by higher incomes and higher levels of educational attainment), death rates go down and life expectancies at birth increase. In essence, rich people tend to live longer than poor people due to any number of factors associated with improved living conditions brought about by higher incomes. In contrast, societies (and minorities within developed societies) suffering from social and economic disadvantages often have lower life expectancies. In the United States, for example, African American women have five times the risk of dying in childbirth as do white women, a clear indication of the differential access to health care. Indeed, current research suggests that socioeconomic status is more important than lifestyle factors in explaining the racial differences in mortality and thus life expectancies. However, the significant improvements in mortality rates in developed nations (across all groups) have considerably raised life expectancies—more than 31 years for females in the United States since 1900. In turn, this has more than doubled the proportion of female babies surviving from birth to age 65, which has led to the increase in the number of older persons in developed countries such as the United States. As the status of women improves in all parts of the world, life expectancy for women can be expected to improve as well.

SEE ALSO: Ethnicity, Maternal mortality, Morbidity, Mortality, Socioeconomic status

Suggested Reading

  • Gribble, J. N., & Preston, S. H. (Eds.). (1993). The epidemiological transition: Policy and planning implications for developing countries. Washington, DC: National Academy Press.
  • Livi-Bacci, M. (2001). A concise history of world population (3rd ed.). Oxford: Blackwell.
  • Murphy, S. (2000). Deaths: Final data for 1998. National Vital Statistics Reports, 48(11).
  • Siegel, J. (2002). Applied demography. San Diego, CA: Academic Press.
  • Weeks, J. R. (2002). Population: An introduction to concepts and issues (8th ed.). Belmont, CA: Wadsworth Thomson Learning.

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