Most significant indicator of feility is

Net reproductive rate is defined as the number of daughters a newborn girl will bear during her life time assuming fixed age specific feility and moality rates It is a demographic indicator NRR of 1 is equivalent to attaining approximately the 2 child norm If NRR < 1, then the reproductive performance of the population is said to below replacement level Reference : Park&;s textbook of preventive and social medicine, 23rd edition, Page no: 489