Life expectancy is the most general and best known measure of the health status of the population. It is defined as the average number of years that a person could expect to live if he or she experienced the age‐specific mortality rates prevalent in a given country in
a particular year. It does not include the effect of any future decline in age‐specific mortality rates. Each country calculates its life expectancy according to somewhat varying methodologies. These methodological differences can affect the exact comparability
of reported estimates, as different methods can change a country's measure of life expectancy slightly.