Demographic and Health Surveys Methodology - Measure DHS

1. Higher age group: A woman’s age at the end of the period determines the higher age group.The higher age group is calculated by subtracting the women’s date of birth from the date ofinterview (in CMC), dividing the difference by 60, and truncating to a whole number. Thenumber of months spent in the higher age group is the difference in months between her ageat the end of the period of exposure (date of interview less one month) and the lower age limitof the age group plus one month. If the number of months in the age group is less than theduration of the time period (36 months), then the woman contributes exposure to both thehigher age group and the next lower age group.2. Lower age group: The contribution to the lower age group is 36 less the number of months inthe higher age group. If the number of months in the higher age group is greater than or equalto the duration of the time period ( 36 months), then the exposure in the higher group is theduration and the exposure in the lower age group is zero.C. Tabulation: Each woman is tabulated twice, once according to her higher age group accumulatingthe exposure she contributes to that group and once in the lower age group accumulating lowerage group exposure. (In ISSA, the same table is used, effectively summing the accumulationswithin each age group.) For ever-married samples, the exposure is adjusted to represent allwomen by dividing by the woman’s “all-woman factor” (AWFACTOR), which is derived fromthe proportion of ever-married women from the household data file. See section on all womenfactors for details in their calculation.D. ExamplesExample 1—A woman interviewed in December 2001, born in May 1970. Her CMC date ofinterview is 12*(2001 – 1900)+12 = 1224. The date of the end of the period of exposure is 1224 –1 = 1223. Her CMC date of birth is 12*(1970 – 1900)+5 = 845. Her age in months at the end ofthe period is 1223 – 845 = 378. The age group at the end of the period is 378/60 = 6.3, truncatedto 6. This represents age group 30–34 years (30 = 6*5 years interval). The number of months inthis age group is 378 – 6*60 + 1 = 19 months. Since this is less than the total number of monthsduring the period (36 months), she contributed 19 months to age group 30–34 during the periodand 36 – 19 = 17 months to the age group 25–29 during the period.Example 2—A woman interviewed in December 2001, born in March 1967. Her CMC date ofinterview is 12*(2001 – 1900)+12 = 1224. The date of the end of the period of exposure is 1224 –1 = 1223. Her CMC date of birth is 12*(1967 – 1900)+3 = 807. Her age in months at the end ofthe period is 1223 – 807 = 416. The age group at the end of the period is 416/60 = 6.93, truncatedto 6. This represent age group 30–34 years (30 = 6*5 years interval). The number of months inthis age group is 416 – 6*60 = 56 months. Since the number of months in this age group is greaterthan 36 months, she contributed 36 months of exposure to age group 30–34 during the period andno exposure to the next lower age group during the period.E. ASWFR—The age-specific wanted fertility rate is calculated as the quotient of the numeratordivided by the denominator for each age group, multiplied by 1000. The result is an average rateover the 36-month period, expressed as an annual rate.F. TWFR—The total wanted fertility rate is calculated by summing the ASWFRs, multiplying by 5,and dividing by 1,000.Guide to DHS Statistics 88 Updated September 2006