Life expectancy

Life expectancy is a statistical estimate of the average amount of time an organism is anticipated to live based on the year of its birth, its present age, and other demographic variables, such as gender. In the United States, the most frequently used metric is life expectancy at birth (LEB), which may be defined in two different ways: Cohort An actual birth cohort (i.e., all people born in a particular year) has a mean length of life (LEB) that can only be calculated for cohorts that were born several decades ago and whose members have all passed away. LEB is the mean length of life of a hypothetical cohort that is supposed to have been exposed to the mortality rates recorded in a particular year from birth to death, from birth to death.

If age-specific death rates continue to stay at their most recently recorded levels, life expectancy may be calculated mathematically as the mean number of years of life that will be left at a particular age at that age. It is represented by the displaystyle e xe x,[a], which denotes the mean number of additional years of life for someone now aged xx, based on a certain mortality event, for someone who is now aged xx. LONGEVITY is not synonymous with maximum longevity, and neither is life expectancy with age. The statistical definition of life expectancy is the average number of years that a person or a group of individuals will have left when they reach a certain age in their lives. Longevity is defined as the features of certain individuals of a population having a particularly long lifetime. The age at which the longest-living member of a species dies is referred to as the species's maximum lifespan. A further consideration is that, since life expectancy is an average, a given individual may die many decades before or after the "anticipated" survival. When it comes to longevity, the phrase "maximum lifetime" refers to something quite different.

Plant or animal ecology, as well as life tables, make use of the term "life expectancy" (also known as actuarial tables). Life expectancy is also used in the context of manufactured objects, though the related term shelf life is more commonly used in the context of consumer products, and the terms "mean time to breakdown" (MTTB) and "mean time between failures" (MTBF) are more commonly used in the context of industrial products.