fertility measures & concepts. complexities of fertility analysis involves 2 individuals of...
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Fertility Measures & Concepts
Complexities of Fertility Analysis
• Involves 2 individuals of opposite sex
• Risk is not universal in female population– Fecundity– Sexual activity– Contraception/abortion
• Repeatable event
Crude Birth Rate
• The CBR is often multiplied by 1,000 and expressed per 1,000 in the population
– The CBR of Malawi from 1985-90 was 56.3
CBR = Births in the period 0 to TPerson-yrs lived 0 to T
(mid-year population)
General Fertility Rate
• The GFR is also often multiplied by 1,000 and expressed per 1,000 in the population
GFR = Births in the period 0 to TPerson-yrs lived 0 to T by women ages 15-50
(mid-year population)
Age-Specific Fertility Rates
ASFR = Births in the period 0 to T to women aged x to x+nPerson-yrs lived 0 to T by women aged x to x+n
Number ofAge Women Births ASFR
15-19 100,000 20,000 0.20020-24 120,000 40,000 0.33325-29 90,000 50,000 0.55630-34 100,000 20,000 0.20035-39 80,000 8,000 0.10040-45 95,000 1,000 0.011
Total Fertility Rate
• Sum of all age specific fertility rates
ASFR0.2000.3330.5560.2000.1000.011
1.399x 5 yrs
TFR=6.997
Variants of TFR
• Parity specific fertility rates– Women at parity “p”
• Marital fertility rates– Married women
Cohort Fertility
• The mean parity for a cohort of women who have completed their fertility is that cohort’s TFR
Parity Progression Ratio
• Proportion of a cohort who had at least i live births who went on to have at least one more
• Box 5.4 (p. 105)
PPR= Number of women at parity i+1 or moreNumber of women at parity i or more
Reproduction Measures
• Gross Reproduction Rate (GRR)– The number of female births an average woman
would have if she lived through the end of her reproductive span.
• Net Reproduction Rate (NRR)– The average number of daughters that female
members of a birth cohort would bear during their reproductive life span if they were subject to the observed age-specific maternity rates and mortality rates through their lifetimes.
– NRR=1 equals exact replacement fertility
Why are high birth rates so low?
Proximate Determinants of Fertility
• Marriage & Marital Disruption
• Sterility
• Postpartum Infecundability
• Fecundability
• Spontaneous Intrauterine Mortality
• Contraception
• Induced Abortion