Net Reproduction Rate
Also known as: NRR, Net reproduction ratio, Net reproductive rate, Net Üreme Hızı
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.
Key highlights
- Directly measures generational replacement by combining fertility and survival, unlike the TFR or GRR which ignore daughter mortality.
- Has a clear and powerful benchmark: NRR equal to one is exactly replacement, with growth above and decline below.
- Connects cleanly to stable-population theory and the intrinsic rate of natural increase through a simple logarithmic relation.
- Removes the influence of current age structure, giving a structure-free read on long-run reproductive potential.
Intuition
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How it works
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When to use it
Use the net reproduction rate when the question is generational replacement — whether the current period's fertility and mortality, if sustained, would lead a population to grow, shrink, or hold steady in the long run. It is the standard input to stable-population theory and the intrinsic growth rate. Assumptions and caveats: the NRR is a period, synthetic-cohort measure that assumes the year's age-specific fertility and female mortality persist unchanged, and it ignores migration. Do NOT read it as the literal experience of a real cohort, and remember it shares the period TFR's vulnerability to tempo distortions when the timing of childbearing shifts. For replacement that abstracts from mortality, use the gross reproduction rate; for total childbearing of both sexes, use the TFR; for real-cohort replacement, use cohort measures.
Strengths & limitations
- Directly measures generational replacement by combining fertility and survival, unlike the TFR or GRR which ignore daughter mortality.
- Has a clear and powerful benchmark: NRR equal to one is exactly replacement, with growth above and decline below.
- Connects cleanly to stable-population theory and the intrinsic rate of natural increase through a simple logarithmic relation.
- Removes the influence of current age structure, giving a structure-free read on long-run reproductive potential.
- It is a period synthetic-cohort measure and so is distorted by tempo effects when the timing of childbearing changes.
- It assumes the year's fertility and mortality schedules persist indefinitely, which rarely holds in practice.
- It ignores migration, which can dominate actual population change even when the NRR is below one.
- It depends on accurate female mortality and the assumed sex ratio at birth, errors in which bias the result.
Common pitfalls
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Applications
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Frequently asked
What is the difference between the gross and net reproduction rates?
The gross reproduction rate (GRR) is the average number of daughters a woman would bear if she survived through all reproductive ages — it ignores mortality. The net reproduction rate (NRR) discounts those daughters by the probability of surviving to each childbearing age. Where female child and adult mortality is low, the NRR is close to the GRR; where mortality is high, the NRR is substantially smaller.
Why does an NRR of one mean replacement?
The NRR is the expected number of surviving daughters per woman. If each woman is replaced by exactly one daughter who herself survives to childbearing, the number of potential mothers stays constant from one generation to the next, so the population neither grows nor shrinks in the long run. An NRR above one means more than one replacement per woman (growth) and below one means fewer (decline).
Can a population still grow when the NRR is below one?
Yes, for a considerable time, because of population momentum. If past high fertility has produced a young age structure with many women entering their childbearing years, births can exceed deaths for decades even though period replacement is below one. The NRR describes the long-run tendency under fixed rates, not the immediate balance of births and deaths in a population that is not yet stable.
Sources
- 1.Preston, S. H., Heuveline, P., & Guillot, M. (2001). Demography: Measuring and Modeling Population Processes. Blackwell.ISBN 9781557864512
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Cite this page
ScholarGate. (2026, June 22). Net Reproduction Rate. ScholarGate. https://scholargate.app/demography/net-reproduction-rate