Average number of years a group of individuals can expect to live.
Life expectancy at birth (or at age 0) represents the mean length of life – i.e. the mean age at death – of a synthetic cohort exposed at each age to the mortality patterns of a given year. It is a measure of mortality that is independent of the effects of age structure. Life expectancy at birth is a particular case of life expectancy at age x, which represents the mean number of remaining years of life beyond age x (or mean survival duration at age x), under the mortality conditions of the year in question.