Sunday, January 15, 2006

life expectancy

The terms life expectancy and life span need to be distinguished from one another because the first refers to the average number of years people actually live, whereas the second applies to the biological limit of human life-l20 years. Although a few people do live past 110 years, and one Japanese man was even recorded as reaching 120, the average person dies at a much younger age-in fact, half the U.S. population dies by age 75.
The dictionary defines life expectancy as "an expected number of years of life based on statistical probability" -a probability that is calculated by examining the survival rate for a specific population (for example, everyone born in 1925 or everyone born in 1990), and then using that as the probability that people in that population will live to a particular year. In the United States the present overall life expectancy for women and men at birth is about 75 years.
Because women live longer than men, however, the rates for the sexes differ-the average is 71.5 years for men and 78.3 for women. White people have a longer life expectancy than black people-the latter average only 69.7 years.
Life expectancy is widely used as a standard for comparing the health and welfare of nations; a comparison that rests on the idea that countries with longer average lifetimes have better nutrition, health care, and so on. In this respect the United States, the wealthiest nation in the world, measures up less well than one might expect when compared to other industrialized nations. Japan, with 77 years, has the highest life expectancy in the world; Sweden ranks second at 76.6 years; and Norway is third at 76.2. Other nations that exceed the United States include Denmark, France, Italy, Canada, Australia, Hong Kong, and Israel-in that order. Other European nations (United Kingdom, West Germany, etc.) match the U.S. closely.
The relatively unfavorable showing of the U.S. is due in part to the high infant mortality that occurs in American minority groups, where many people are afflicted with poverty, disease, lack of education, inadequate prenatal care, and the social and family disorganization that typically accompanies such conditions. It is also true that the nations that lead the world in life expectancy are those with relatively little cultural or ethnic diversity-nations that can be described as having homogeneous populations.
Over the centuries average life expectancy has increased from about age 20 in ancient Rome some 2,000 years ago (death in childhood and youth were common there owing to the lack of sanitation and medical know-how) to about age 40 at the time that the pilgrims came to America. Between the time of the pilgrims and 1900, life expectancy in America grew slowly to about age 47. After the turn of this century it exploded with an increase to 75 years, an unprecedented jump of almost 30 years between 1900 and 1975. The most recent increases-those that occurred after 1960 -- have been due in part to better medical control of cancer, heart disease, and stroke. This advance, together with earlier progress, has brought the proportion of Americans over age 65 from 4 percent of the population and three million people in 1900 to about 12 percent of the total and 30 million people at the present time. The U.S. Bureau of the Census projects an even more rapid expansion of the 65 population until the middle of the next century, when growth will level off at 67.5 million and at 21.8 percent of the population.
The most explosive period of growth for people aged 65 will occur after 2010, as shown by the following proportions and numbers of people over that age at various intervals: year 1990---about 12.7 percent and 31.5 million; year 2000---13 percent and nearly 35 million; year 2010---13.8 percent and 39 million; year 2020---17.3 percent and 51.5 million; year 2030---21.2 percent and 64.5 million; year 2040---21. 7 percent and 67 million.
Schick, F. L. Statistical Handbook on Aging Americans. Phoenix: Oryx Press, 1986.
U.S. Bureau of the Census. An Aging World. International Population Reports Series P-95. No. 78. Washington, D.C.: U.S. Government Printing Office, 1987.


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