Life tables are constructed on the basis of a single cross-sectional time data for a generation. There is also a longitudinal life table method which takes a real cohort of persons that start life at a specific age interval and follow it throughout life until they die.
Further, a complete life table may be constructed on the basis of single years of ages.Age specific mortality rates are applied to a notional population, typically of 100,000. Starting at birth, the probability of dying in each period is applied to the number of people surviving to the beginning of the period, so that the initial figure slowly reduces to zero.
An abridged life table can also be constructed wherein ages are grouped in 5 or 10 years of interval, taking the intial year as 0-1.
Such a life table is based on current age-specific death rates for each age or age band used and are called period life tables and are the most frequently used type.
From Investopedia and HealthKnowledge.
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