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