Compare methods

	Inverse Projection	Family Reconstitution
Field	Historical Demography	Historical Demography
Family	Process / pipeline	Process / pipeline
Year of origin	1981	1956
Originator	Ronald Lee; E. A. Wrigley and R. S. Schofield; generalized by Jim Oeppen	Louis Henry and Michel Fleury; refined by E. A. Wrigley and R. S. Schofield (Cambridge Group)
Type	Demographic reconstruction from aggregate flows	Nominative record-linkage and demographic estimation
Seminal source	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., Davies, R. S., Oeppen, J. E., & Schofield, R. S. (1997). English Population History from Family Reconstitution 1580-1837. Cambridge University Press. ISBN: 9780521590150
Aliases	Back projection, Generalized inverse projection, Demographic back-projection, Lee-Wrigley-Schofield projection	Parish register reconstitution, Nominative family linkage, Henry-Fleury method, Cambridge Group reconstitution
Related	4	4
Summary	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.	Family reconstitution is the nominative technique that rebuilds the demographic experience of historical communities by linking individual baptism, marriage and burial entries from parish registers into the reproductive and mortality histories of identifiable families. Developed by Louis Henry and Michel Fleury in 1950s France and brought to its fullest expression by the Cambridge Group for the History of Population and Social Structure under Wrigley and Schofield, the method transforms an undifferentiated stream of vital events into Family Reconstitution Forms, each documenting a marriage, the births of children, and the deaths of family members. From these forms the analyst derives age-specific fertility, age at marriage, birth intervals, infant and child mortality, and adult survivorship. Because it works at the individual level it can isolate demographic behaviours—such as spacing or stopping—invisible to aggregate counts, making it the gold standard for pre-census population history.