Abridged Life Table

The abridged life table is the workhorse of demography and population health for summarizing the mortality experience of a population in a single, age-grouped table. Instead of a single-year (complete) life table, it works on broad age intervals — typically <1, 1-4, then five-year groups up to an open-ended oldest interval — which makes it robust when deaths or populations in single years of age are sparse or noisy. The construction propagates a small set of inputs, the age-specific death rates nMx, through a chain of columns: the probability of dying nqx, the survivors lx, the deaths ndx, the person-years lived nLx and Tx, and finally life expectancy ex. Chiang's 1984 treatment supplied the standard estimator and the fraction-of-interval term ax that controls how person-years are allocated within each interval, while Preston, Heuveline and Guillot's 2001 textbook codified the modern pipeline used across demography and epidemiology.