Transcript Fertility Measures & Concepts Complexities of Fertility Analysis • Involves 2 individuals of opposite sex • Risk is not universal in female.

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
CBR = Births in the period 0 to T
Person-yrs lived 0 to T
(mid-year population)
• 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
General Fertility Rate
GFR = Births in the period 0 to T
Person-yrs lived 0 to T
by women ages 15-50
(mid-year population)
• The GFR is also often multiplied by 1,000
and expressed per 1,000 in the population
Age-Specific Fertility Rates
ASFR = Births in the period 0 to T to women aged x to x+n
Person-yrs lived 0 to T by women aged x to x+n
Age
15-19
20-24
25-29
30-34
35-39
40-45
Number of
Women
100,000
120,000
90,000
100,000
80,000
95,000
Births
20,000
40,000
50,000
20,000
8,000
1,000
ASFR
0.200
0.333
0.556
0.200
0.100
0.011
Total Fertility Rate
• Sum of all age specific fertility rates
ASFR
0.200
0.333
0.556
0.200
0.100
0.011
1.399
x 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
Number of women at parity i+1 or more
PPR= Number of women at parity i or more
• 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)
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
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Marriage & Marital Disruption
Sterility
Postpartum Infecundability
Fecundability
Spontaneous Intrauterine Mortality
Contraception
Induced Abortion