The life table

The main part of this book starts where demography itself started, with the life table. The life table is couched in terms of probabilities for individuals, but for populations it is a deterministic model of mortality and survivorship. That it presents expected values and disregards random variation is contrary to the way nature works and, in particular, oversimplifies demographic mechanisms, yet a rich variety of useful results is based on it. A method is valuable in direct proportion to the substantive conclusions to which it leads, and in inverse proportion to its complexity