Hey there
the answer is Life expectancy is a statistical measure of the average time an organism is expected to live, based on the year of their birth, their 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 birthcohort (all individuals born a given year) and can be computed only for cohorts born many decades ago, so that all their members have died.
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