Life expectancy ex is the average life expectancy at the age of X, which represents the average number of years (or ages) that survivors at the age of X can expect to live in the future. It is the main index to evaluate the health status of residents. Life expectancy at birth (0-year-old group), referred to as average life expectancy, is a comprehensive reflection of the impact of mortality in various age groups and can generally explain the health level of a certain population.