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	Mean Age at Childbearing	Net Reproduction Rate
Field	Demography	Demography
Family	Process / pipeline	Process / pipeline
Year of origin	1968	2001
Originator	Standard demographic practice (fertility schedule moments)	Richard Böckh and Robert Kuczynski (formalized in Preston, Heuveline & Guillot)
Type	Summary location measure of the age pattern of fertility	Period measure of generational replacement combining fertility and mortality
Seminal source	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
Aliases	MAC, Mean age of the fertility schedule, Mean age of mothers at birth, Ortalama Doğurganlık Yaşı	NRR, Net reproduction ratio, Net reproductive rate, Net Üreme Hızı
Related	4	4
Summary	The mean age at childbearing is the average age of mothers at the birth of their children, computed as the fertility-rate-weighted mean of maternal age over the age-specific fertility schedule. As the first moment of the fertility curve, it summarizes the tempo — the timing — of childbearing in a single number, complementing the total fertility rate, which measures quantum, or how many children are born.	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.