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Multilingual Demographic Dictionary, second unified edition, English volume
Death function
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To the survivors function corresponds a death function 1 which is calculated as the differences between the number of survivors (432-4) at different ages. It is named the distribution of life table deaths 2★ in order to be distinguished from the crude distribution of deaths. Life tables typically include the expectation of life 3 or life expectancy 3 at age x ; this is the mean number of years to be lived by those surviving to exact age x, given the mortality conditions of the table. The expectation of life at birth 4 is a particular case of expectation of life, and represents the mean length of life 4 of individuals who have been subjected since birth to the mortality of the table. The reciprocal of the expectation of life at birth is the life table death rate 5 or death rate of the stationary population 5.
- 3. By integrating the survivorship function (432-3) between two exact given ages we obtain the total number of years lived by the cohort between these ages; the notation for the total number of years lived between age x and x + n is nLx . This function is often called the stationary population in life table column headings. By summing it from a given age x to the end of life, we obtain the total number of years to be lived after attaining age x by those reaching that age; the conventional notation is T x .
- 4. The notation for the expectation of life at age x is ex