Net reproduction rate (NRR) is the average number of daughters that would be born to a woman during her lifetime if she passed through her lifetime from birth to the end of her reproductive years conforming to the  age-specific fertility rates (ASFR) and mortality rates of a given year. NRR is always lower than GRR because it takes into account the fact that some women will die before entering and completing their childbearing years. Also, NRR will be less than half the magnitude of the TFR. Replacement level  fertility is said to have been reached when NRR=1.0 ( total fertility rate (TFR);  gross reproduction rate (GRR);  fertility replacement).