مقایسهٔ روش‌ها

	Inverse Projection	Historical Life Table Construction
حوزه	Historical Demography	Historical Demography
خانواده	Process / pipeline	Process / pipeline
سال پیدایش	1981	1662
پدیدآور	Ronald Lee; E. A. Wrigley and R. S. Schofield; generalized by Jim Oeppen	John Graunt (origins); Coale, Demeny, Ledermann (model life tables); applied by Wrigley-Schofield and Bengtsson
نوع	Demographic reconstruction from aggregate flows	Mortality estimation and survivorship modelling
منبع بنیادین	Wrigley, E. A., & Schofield, R. S. (1981). The Population History of England 1541-1871: A Reconstruction. Edward Arnold / Harvard University Press. ISBN: 9780674690073	Wrigley, E. A., & Schofield, R. S. (1981). The Population History of England 1541-1871: A Reconstruction. Edward Arnold / Harvard University Press. ISBN: 9780674690073
نام‌های دیگر	Back projection, Generalized inverse projection, Demographic back-projection, Lee-Wrigley-Schofield projection	Historical mortality table building, Model life table fitting, Survivorship reconstruction, Paleodemographic life tables
مرتبط	4	4
خلاصه	Inverse projection, and its more flexible successor generalized inverse projection, reconstructs the demographic history of a population from the outside in. Where conventional cohort-component projection runs a known population forward using assumed rates, inverse projection runs the logic backward: starting from a population of known size and age structure at one date, and given annual totals of births and deaths, it infers the population sizes, age distributions, mortality levels, life expectancies and fertility rates that must have prevailed in earlier years. The technique was devised by Ronald Lee and applied by Wrigley and Schofield to their English aggregative series, allowing three centuries of population history to be recovered without any direct census before 1801. Jim Oeppen's generalization relaxed restrictive assumptions about migration and closed populations. The method is the bridge that turns raw counts of vital events into a fully articulated demographic regime.	Historical life table construction is the craft of converting the patchy mortality evidence of the past—burial registers, family genealogies, monastic obituaries, even skeletal age-at-death distributions—into the formal apparatus of the life table: age-specific death rates, the probability of dying within each age interval, the number of survivors to each age, and expectation of life. The life table descends from John Graunt's 1662 reading of London's Bills of Mortality and Halley's Breslau table, but applying it to historical populations demands special care, since exposures are rarely known and deaths are often recorded without reliable ages. Historians therefore lean heavily on families of model life tables to smooth noisy data and fill missing age bands. Whether built as period tables capturing a single era's mortality or cohort tables following one birth-year group through life, these reconstructions are the indispensable summary of how, and how long, people lived in the past.