There are two characteristics of the life span today that distinguish it from the pattern that existed several generations ago. First, the heavy preponderance of young people no longer exists. Instead, as more and young people no longer exists. Instead, as more and more people live to be older, the proportions of individuals at different age levels becomes increasingly similar. It is estimated that, in time, the proportions will be approximately equal.

The explanation for this change is that there are fewer children being born today than in the past, due to improved methods of contraception, and that better health and medical care enables more and more people to live longer. There is, however, a difference between the sexes in number of people at every age level, with females outnumbering males, especially in the latter years of life.

The second characteristic of the life span is that American men and women, on the average, live longer than men and women of any other country and longer than men and women in the United States in past generations. In 1900, for example, the life expectancy for white males was 48.2 years; for white females, it was 51 years. By 1970, the life expectancy for white males had risen to 67.5 years, and for white females it has risen to 74.1 years. For blacks and other minority groups, the life expectancy for both males and females was several years less. It has been estimated that by 1990. 9.4 percent of the entire American population will be over sixty-five years of age.

Many factors influence the length of the life span; the most important of these are given below.

It has never been possible to predict how long a given individual will live. This is just as true today as in the past. However, Scheinfeld has suggested that if three factors are taken into consideration, a general prediction is possible. According to him:

How long you, personally, may expect to live depends on these principal influences: First, environment – the way in which you were started off in life and the conditions under which you lived thereafter and live now. Second, your inherited vigor or weakness (as applied both to specific diseases and defects and to general resistance factors), with particular attention to your sex. And, third, luck.

Conditions Influencing Longevity
  • Heredity. Longevity tends to run in families.
  • Physical Characteristics. People of average size and body structure tend to live longer than those who are under – or overweight or who are very tall or very short.
  • General Physical Condition. A good physical condition throughout life, but especially during the growth years of childhood and adolescence, is favourable to longevity.
  • Sex. Women, as a group, outlive men.
  • Race. In America, blacks, Puerto Ricans, and other minority-group members have a shorter life expectancy than whites.
  • Geographic Location. People who live in urban and suburban areas tend to live longer than those who live in rural areas as a result of better health and medical facilities.
  • Socioeconomic Level. The higher the socioeconomic level, the longer the individual’s life span tends to be.
  • Intelligence. Individuals with high intelligence and those with intellectual interests live longer than less intelligent.
  • Education. People who are better educated tend to live longer than those whose education is limited.
  • Smoking and Drinking. Nonsmokers and non-drinkers tend to live longer than those who smoke and drink excessively.
  • Marital Status. Those who are or have been married live longer than those who have never been married.
  • Efficiency. Those who are efficient tend to live longer than the inefficient because they expend less energy in whatever they do.
  • Anxiety. The tendency to suffer from anxiety due to work, family, economic or other problems leads to hypertension which shortens the life span.
  • Occupation. The kind of work the individual does affects the length of the life span.
  • Happiness. People who are reasonably happy and satisfied with the pattern of their lives normally live longer than those who are dissatisfied and unhappy.