<P> Life expectancy is a statistical measure of the average time an organism is expected to live , based on the year of its birth , its current age and other demographic factors including gender . The most commonly used measure of life expectancy is at birth ( LEB ) , which can be defined in two ways . Cohort LEB is the mean length of life of an actual birth cohort ( all individuals born a given year ) and can be computed only for cohorts born many decades ago , so that all their members have died . Period LEB is the mean length of life of a hypothetical cohort assumed to be exposed , from birth through death , to the mortality rates observed at a given year . </P>
<P> Life expectancy is a statistical measure of the average time an organism is expected to live , based on the year of its birth , its current age and other demographic factors including gender . The most commonly used measure of life expectancy is at birth ( LEB ) , which can be defined in two ways . Cohort LEB is the mean length of life of an actual birth cohort ( all individuals born a given year ) and can be computed only for cohorts born many decades ago , so that all their members have died . Period LEB is the mean length of life of a hypothetical cohort assumed to be exposed , from birth through death , to the mortality rates observed at a given year . </P>
life expectancy is the average age at death of the
life expectancy is the average age at death of the
cohort
cohort