What does life expectancy measure?
the average income a population likely earns during employment
the average human development during a population's lifetime
the average number of years that a population is likely to live
the average standard of living during a population's lifetime

Life expectancy measures the average number of years that a population is likely to live.

Explanation:

Life expectancy is the average life expectancy of all persons in a geographical area or a population group. The average age is calculated by summing the age of all who die within a year and dividing the number by the number of deaths. In America, for example, life expectancy is 78.6 years.

Life expectancy has increased globally in the 20th century as a result of the medical revolution. Various medical developments mainly explain the rise in life expectancy to the present level, but have also been influenced, for example, by the availability and quality of food.