Life expectancy is a statistical measure of the average number of years of life remaining for a person of any given age. This measure is based on the death rates by age for a specific population at a specific time, usually a calendar year. It assumes that death rates will not change in the future. If death rates decline, as has normally happened, life expectancy increases. When death rates increase, life expectancy declines. Social scientists and health workers use life expectancy to summarize the overall health of a population.
The table with this article compares the life expectancies at birth for males and females living in various countries. Life expectancy varies from country to country because of differences in public health and standards of living . Industrialized nations have the highest life expectancy, and the less developed countries, especially those in Africa, have the lowest. With few exceptions, females have a higher life expectancy than males.
Since 1900, three major changes have taken place in life expectancy in the United States . First, life expectancy at birth has increased by over 30 years—from 47.3 years in 1900 to 81.2 years in 2018. Second, the gap in life expectancy between the sexes has widened. In 1900, newborn girls could be expected to live two years longer than newborn boys. In 2018, girls could be expected to live about five years longer. Third, the difference in life expectancy between white Americans and nonwhite Americans has decreased. In 1900, whites could be expected to live 14.6 years longer than nonwhite Americans. In 2018, the difference between white and nonwhite Americans was about 4 years.
