Demographic and Health Surveys Methodology - Measure DHS

DHS uses century month codes extensively during the process of editing and imputing data. Theadvantages of the approach include the following:• When checking for consistency, use of the century month codes makes it easy to check not only thatthe events occurred in chronological order, but also that there should be a minimum interval betweenthem. For example B3(2)—B3(1) should be greater or equal to 9 months (the duration of apregnancy).• For imputation 4 purposes, if information were missing between two events, the random imputationwould be quite reasonable. For example, if date of birth for the second child is unknown, that birthshould have occurred between the first birth plus nine months, and nine months before the third birth.The lower and upper limits for a random number generator are plausible.Random (B3(1) + 9, B3(3) – 9) , Random (1192, 1202)The use of CMC at the analysis phase facilitates the calculation of intervals or ages at different events.Throughout all DHS analysis computer programs, instructions like the ones shown below are verycommon.Respondent’s age = int( (DOI – DOB)/12 )(1220 – 952)/12 = 22 years oldAge at first birth = int( (DBC1 – DOB)/12 )(1183 – 952)/12 = 19 years oldAge at sterilization = int( (DOS – DOB)/12 )(1216 – 952)/12 = 22 years oldAge of last child in months = DOI – DBC31220 – 1211 = 9 monthsInterval between birth 1 and 2 = DBC2 – DBC11198 – 1183 = 15 monthsMonths since sterilization = DOI – DOS1220 – 1216 = 4 monthsDHS recommends that analysts use the century month code variables when dealing with intervals or agesat different events.Median CalculationsThere are four different types of median calculations in DHS statistics, and results vary according to thetype of variable being analyzed.Medians for completed time periods. These are medians for variables such as intervals between eventsor ages calculated at different events; for example, current age, age at first union, and age at sterilization.Medians for this type of variables take into consideration that ages are given in completed years. Arespondent who is currently 20 years old could be somewhere between 20 years and 1 day old or 20 yearsand 364 days old.Medians for continuous variables. These are medians for variables such as children’s weight at birth orany other type of measurement in the continuous scale.4 Croft, T. 1991. Date Editing and Imputation. Demographic and Health Surveys World Conference Proceedings, II: 1337–1356, Columbia,Maryland: IRD/ORC Macro.Guide to DHS Statistics 16 September 2003