Life Expectancy

Life expectancy, is the average length of time that a person of a certain age can expect to live thereafter. The most common measure of life expectancy is life expectancy from birthLife expectancy is a hypothetical metric. It assumes that age-specific mortality rates for the year in question will be valid throughout the lifetimes of individuals born in that year. The estimation actually reflects age-specific mortality (death) rates over the entire lifetime of the population born (or living) during a given period of time. Size varies significantly by age, gender, race, and geographic location. Therefore, life expectancy is given for specific categories rather than population in general. For example, the life expectancy of white women born in 2003 in the United States is 80.4 years.

Life expectancy varies with local conditions. In less developed countries, life expectancy at birth is lower compared to more developed countries due to unfavorable living conditions and natural conditions. In some underdeveloped countries, life expectancy at birth may be lower than life expectancy at 1 year, due to high infant mortality rates (usually due to infectious disease or difficulty in accessing a clean water source).

Life expectancy is calculated by creating a life table. The life table contains data on the age-specific death rates for that population, which requires census data for the number of deaths for that population at all ages and for the number of people. These numbers are typically derived from the national census and vital statistical data from which the average life expectancy for each age group in the population can be calculated.

The accuracy of the estimated life expectancy depends on the completeness of the census and death data available for the population in question. The completeness of these data differs from country to country. In the United States, for instance, official full life tables based on recorded deaths have been produced in conjunction with the ten-year census since 1900. Since 1945, annual abbreviated US life tables have been published based on annual death records and population estimates. Full life tables show life expectancy for each age and abbreviated tables show life expectancy for age groups of 5 or 10 years rather than single-year groups. For many countries, national life tables are published by the United Nations in their Demographic Yearbook.

Another method of calculating life expectancy is healthy life expectancy (or disability-free life expectancy), which is the average number of years a person can be expected to live without ill health or disability, given current age-specific death rates, disability, and disease prevalence. Calculating these figures requires census and death data, as well as reliable health statistics.