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	Parity Progression Ratio	Net Reproduction Rate
分野	人口学	人口学
系統	Process / pipeline	Process / pipeline
提唱年	1953	2001
提唱者	Louis Henry (formalized in modern demography)	Richard Böckh and Robert Kuczynski (formalized in Preston, Heuveline & Guillot)
種類	Order-specific fertility measure built from a sequence of conditional progression probabilities	Period measure of generational replacement combining fertility and mortality
原典	Preston, S. H., Heuveline, P., & Guillot, M. (2001). Demography: Measuring and Modeling Population Processes. Blackwell. ISBN: 9781557864512	Preston, S. H., Heuveline, P., & Guillot, M. (2001). Demography: Measuring and Modeling Population Processes. Blackwell. ISBN: 9781557864512
別名	PPR, Birth progression ratio, Parity progression probability, Doğum Sırası İlerleme Oranı	NRR, Net reproduction ratio, Net reproductive rate, Net Üreme Hızı
関連	4	4
概要	A parity progression ratio is the conditional probability that a woman who has already had a given number of children goes on to have one more. By converting a static parity distribution into a sequence of birth-by-birth transition probabilities, the method reveals where childbearing stops within a cohort and lets demographers rebuild completed fertility from the bottom up. It is the natural fertility analogue of a survival or life-table transition, treating each additional birth as a further step a woman may or may not take.	The net reproduction rate (NRR) is the demographic measure of generational replacement: the average number of daughters a woman would bear who survive to the age their mother was when she bore them, given the period's age-specific fertility rates and female mortality. By combining fertility with survival, the NRR answers the fundamental question of whether a population is replacing itself — an NRR of one means each generation of women exactly reproduces the next, below one signals long-run decline, and above one signals growth.