Life expectancy is a statistical measure of the estimate of the span of a life. It refers to the number of years a person can expect to live, based on an estimate of the average age that members of a particular population group will be when they die. The most commonly used measure is life expectancy at birth (LEB), which can be defined in two ways. Cohort LEB is the mean length of life of a birth cohort, and period LEB is the average length of life for a hypothetical cohort assumed to be exposed, from birth through death, to the mortality rates observed at one particular period. Life expectancy is one of the most frequently used health status indicators, and gains in life expectancy at birth can be attributed to a number of factors, including rising living standards, improved lifestyle and better education, as well as greater access to quality health services.

Here are some key points about life expectancy:

• Life expectancy is not the same as longevity or maximum lifespan. Longevity refers to the relatively long lifespan of some members of a population, while maximum lifespan is the age at death for the longest-lived individual of a species.
• Life expectancy is an average, so a particular person may die many years before or after the expected survival.
• Life expectancy is used in measuring the Human Development Index (HDI) of each nation along with adult literacy, education, and standard of living.
• Life expectancy can be calculated by integrating the survival curve from 0 to positive infinity or by averaging the ages at death for an extinct or completed cohort.
• Life expectancy at birth in the United States was 76.4 years for both sexes in 2021, with males having a life expectancy of 73.5 years and females having a life expectancy of 79.3 years.
• Life expectancy at birth in the United States declined nearly a year from 2020 to 2021, according to new provisional data from the CDC’s National Center for Health Statistics (NCHS).
• The United Nations estimate a global average life expectancy of 72.6 years for 2019, and the global average today is higher than in any country back in 1950.