Author:
Visanich Valerie,Bruckner Tim A.
Abstract
Life expectancy, the key metric for assessing current population health, measures the mean age of death for a specified population. Scientists use this summary measure to test hypotheses regarding causes of population health and to compare the mortality experience across regions, defined subgroups, and time. Demographers operationalize life expectancy in two ways: by period and by cohort. This entry explores the difference between period life expectancy (measured as the mean age of death of a hypothetical cohort whose members are born in a reference period) and cohort life expectancy (measured as the mean age at death for a true cohort born in a reference period and followed over the entire life span of its members until none remains alive). The entry also sheds light on making sense of behavioral and societal causes of life expectancy variations, particularly across different countries.