Time-Specific Life Tables Contrasted with Observed Survivorship

Abstract

An exposition of the differences between the 2 basic types of life tables: the time-specific or static type, and the generation or fluent type. The time-specific life table classifies a population at a fixed date into age groups and presents death rates for each age group. The generation type starts with a group of individuals born at approx. the same time and follows them throughout life until all have died, rates of death being computed at each age for those of the original group who survive to that age. The 2 types will in most instances be quite different in form, and in any case will be quite different in meaning. The author emphasizes the error in the fairly common practice of comparing a time-specific life table with a generation one.