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Expectation at birth

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Expectation at birth  (EXPECTATION at birth)

By integrating the survivorship function (431-3) between two given ages we obtain the total number of years lived1 or total lifetime1 of the cohort between these ages. By summing this function from a given age x to the end of life, we obtain the total number of years lived after attaining age x by those reaching this age, which is sometimes called the total after lifetime2. This figure, divided by the number of survivors to age x, would then be called the mean after lifetime; it is the expectation of life3 or life expectancy3 at that age. The expectation of life at birth4 is also called the mean length of life4. The reciprocal of the expectation of life at birth is occasionally used as an index of mortality under the name of life table death rate5. The expectation of life of an individual at age x is sometimes called his life potential6 and the life potential of a population is the sum of the life potentials of its members.

  • 1. The notation for the total number of years lived between ages x and x + n is nLx.
  • 2. The notation for the total after lifetime at age x is Tx.
  • 3. The notation for the expectation of life at age x is e°x.