subtracting dates in stata to calculate age

#Subtracting dates in stata to calculate age full#
#Subtracting dates in stata to calculate age code#

The century day code is analogous to the century month code and gives the number of days since the beginning of 1900. To do this, DHS introduced a new concept – the century day code (CDC).

In DHS-7, The DHS Program introduced the calculation of age taking into account the day of birth and the day of interview. The CMC date of birth (B3) is calculated using a combination of the reported month and year of birth and reported age for living children as well as an imputation process for incompletely or inconsistently reported information. Where V008 is the century month code 2 (CMC) of the date of interview, and B3 is the CMC for date of birth of the child. Previously, DHS calculated age for children by subtracting the month and year of birth from the month and year of interview to give age in months.įor analysts, the age of the child in months was calculated as follows: The quality of date and age reporting has improved over time and by the start of DHS-7, The DHS Program felt that the quality was sufficient to introduce the collection of day of birth and capture sufficiently reliable data. For this narrow group, the quality of data was acceptable but was not previously considered good enough for older children or for children who had died.

The exception to this was the collection of day of birth for living children under the age of 5 who live in the household in order to be used in the anthropometric calculations. Historically DHS has not collected the day of birth of all children as the quality of reporting of dates of births and ages was simply not good enough to use more accurate calculations of age. Note that for anthropometry a different procedure is used and age in days is calculated as part of the creation of the anthropometric indices, but this is restricted to living children under the age of 5 that were reported as living in the household. For most analyses, this difference has very little effect, but for a few, it can matter. Similarly, a birth in May 2016 would be considered as 12 months (1 year) old in May 2017, but if the birth is on May 3, 2016, and the interview on May 3, 2017, then the child is 11 months (0 years) old. Thus, if the day of birth is greater than the day of interview (roughly half of all cases) then the age would be over-estimated by one month. For example, a child born February 2017 was considered as 3 months old in May 2017, however, if the birth took place on February 25, 2017, and the interview was May 3, 2017, then the child is actually only two completed months old. Calculating age in months using just month and year of birth and month and year of interview meant that age in months could be off by one month in approximately half of all cases. Why was day of birth added for children in DHS-7?Īdding day of birth permits calculating the age of children more accurately. Additionally, it may also have been reported by a different respondent than the mother of the child. Note that while DHS had previously collected day of birth for children weighed and measured, these data were not used in conjunction with the birth history data as they were not available for a) children who had died, b) children of the respondent who did not live in the household, c) older children, and d) children for whom height and weight was not collected if it was only collected in a subsample of the households. Beginning with the DHS-7 questionnaires, (surveys with fieldwork in about 2015 and later), the woman’s questionnaire collects the day of birth for all children listed in the birth history (all children of the respondents to the woman’s questionnaire) in addition to their month and year of birth.

As part of the biomarker data collection, day of birth was also collected for children age 0-5 years and was used in the calculation of the anthropometric indices.

#Subtracting dates in stata to calculate age full#

More precise calculation results in a shift in ageĬlick here to download the full documentation įor most of DHS history, the DHS woman’s questionnaire collected month and year of birth of the respondent and her age, month and year of marriage or age at marriage, and month and year of birth of each of her children as well as the age of living children.

What has been added to the datasets, and what’s changed?.

Why was day of birth added for children in DHS-7?.

Get all of your questions answered about what changed, why the change happened, and how this might affect your analysis. The calculation of children’s age has recently changed in DHS surveys.