Demographic and Health Surveys Methodology - Measure DHS

WANTED FERTILITY RATESStatistics: Age-Specific Wanted Fertility Rate (ASWFR) and Total Wanted Fertility Rate(TWFR): Based on Age-Period RatesDefinitionA. Coverage: All women aged 15–49 years in seven five-year age groups (15–19, 20–24, 45–49 years).B. Numerators: Number of wanted births that occurred in the 1–36 months-period before the surveyto women in the age group at the time of the birth.C. Denominators: Number of women-years of exposure in the 1–36 month-period before the surveyof women in the age group.D. The age-specific wanted fertility rates (ASFWRs) are the quotients of the numerators divided bythe denominators. The total wanted fertility rate (TWFR) is the sum of the seven age-specificwanted fertility rates multiplied by five.CalculationA. Numerator: Births are tabulated according to period of birth, age of mother at the time of thebirth, and wantedness of the birth.1. Period of birth—The period of birth is calculated as the difference in months between thedate of interview and the date of birth, both in century-month code format (CMC). Births areincluded in the tabulation if they occur 1 to 36 months before the survey.2. Age of mother at the time of the birth—The difference in months between the date of birth ofthe child and the date of birth of the mother, both in CMC. The difference is then divided by60 and truncated to whole numbers to form the age groups. Births are tabulated by age group.3. Wantedness—A birth is considered wanted if the number of living children at the time ofconception of the birth is less than the ideal number of children as reported by the respondent.For the calculation of the time of conception, nine months are subtracted from the date ofbirth. A preceding child is considered living at the time of conception if it was born beforethe date of conception and a) is living at the time of the survey or b) died at or before the dateof conception (calculations based on century-month codes). The date of death of precedingchildren who died is calculated by adding the age at death in months to the child’s birth datein century-month code. If a child’s age at death is reported in years, then the child is assumedto have died at ages 6 months higher than the number of years (30 months for children whodied at 2 years of age, 42 months for children who died at 3 years of age, etc.).B. Denominator: Woman-years of exposure is calculated as the sum of the number of monthsexposed in the five-year age group during the time period. A woman can contribute exposure tojust two five-year age groups during the 36-month period.Guide to DHS Statistics 87 Updated September 2006