Thursday, August 27, 2015

Measures of Reproduction

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Gross Reproduction Rate (GRR):
After the TFR comes GRR. It is restricted to the number of female children. The value of the GRR is about half of the TFR.
It indicates the number of daughters each woman can bear by the time her reproductive period is over if she continues to have children according to a particular schedule of age specific fertility rates, throughout her reproductive period.
According to THOMPSON and LEWIS, 'Whereas TFR includes all births, both male & female, the GRR shows how many girl babies (potential future mothers) could be born to 1000 women passing through their childbearing years, if the age specific birth rate (ASBR) of a given year remained constant and if no woman entering the childbearing period dies before reaching 49.'

Net Reproduction Rate (NRR):
NRR is the average number of daughters that a woman will bear if she experiences a given set of age specific fertility rates throughout the reproductive ages with allowance made for mortality of women over their reproductive years.

which is the probability of daughters surviving to their mother's age.
Different cases of NRR:
i. NRR = 1 signifies exact replacement of one daughter per woman.
Women are bearing just efficient daughters to replace census in future. The replacement level is always reforest to NRR = 1 irrespective of whether population has high or low mortality.
ii. NRR < 1 denotes replacement fertility where fewer daughters to succeed their mother' generation. Any value less than 1 is not replacing exactly.
iii. NRR > 1 denotes above replacement fertility. The future generation of potential mother will be larger than the one that produced them.
NRR is similar to GRR except that it allows for mortality. It is, therefore, always less than GRR.

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