How is life expectancy measured?
Life expectancy is calculated as an average number. Using national death certificates and other survey data in conflict environments, age at time of death is summed and then divided by the total population number.
Life expectancy does not, however, take into account disparities between the very rich and very poor, who may have much huge differences in life longevity. These disparities are not truly captured by a top-life average life expectancy number.
Large health disparities are not captured by average life expectancy data. Long life expectancies may not necessarily reflect quality of life and human development.