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siblings with missing information from the analysis, the information on the birth order of siblings in
conjunction with other information is used to impute the missing data. 1
The distribution of year of birth of respondents in relation to their siblings is another crude
measure of the quality of data. If there is no bias in reporting, the year of birth of siblings should be
roughly equivalent to the year of birth of respondents overall. The distribution of respondents and their
siblings by year of birth is close, with the median year of birth of respondents just one year more than
that of siblings (1960 versus 1959), indicating that there is no serious underreporting of siblings
(Appendix Table C.8).
Yet another crude measure of data quality is the mean number of siblings, or the mean sibship
size (Appendix Table C.9). Sibship size is expected to decline as fertility declines over time. The absence
of a monotonic decline in sibship size, even though fertility has declined in Ethiopia, is an indication that
there may be some omission in the reporting of older siblings. This is also confirmed by the sex ratios
that are larger than the internationally accepted sex ratio of 103-105, especially further back in time,
indicating that either sisters are underreported or brothers are overreported. However, since adult
mortality rates are reported here for the seven years preceding the survey, this omission is unlikely to
affect the calculation of mortality rates. Moreover, if the omission occurred mostly among sisters who
did not survive to adulthood (which is most likely the case), it may not even bias the estimation of
maternal mortality. Nevertheless, it should be borne in mind that any information that relies on recall
of events will suffer from some degree of misreporting, especially if it pertains to deceased persons and
occurred a long time before the survey.
9.2 ADULT MORTALITY
It is advisable to begin by estimating overall adult mortality. If the overall mortality estimates
display a general, stable, and plausible pattern, it lends credence to the maternal mortality estimates
derived thereafter. This is simply because maternal mortality is a subset of adult mortality.
Direct estimates of male and female adult mortality are obtained from information collected in
the sibling history. Age-specific death rates are computed by dividing the number of deaths in each age
group by the total person-months of exposure in that age group during a specified reference period. In
total, female respondents to the Ethiopia DHS reported 91,804 siblings, of whom 43,933 were sisters
and 47,872 were brothers (Appendix Table C.7). Direct estimates of age-specific mortality rates for
males and females are shown in Table 9.1. To minimize the impact of possible heaping on years since
death ending in zero and five, direct estimates are presented for the period 0-6 years before the survey,
which roughly corresponds to 1993-1999. Although the number of sibling deaths during the period
1 The imputation procedure is based on the assumption that the reported birth ordering of the siblings in the
birth history is correct. The first step is to calculate birth dates. For each living sibling with a reported age and for
each dead sibling with complete information on both age at death and year of death, the birth date is calculated.
For a sibling missing these data, a birth date is imputed within the range defined by the birth dates of the bracketing
siblings. In the case of living siblings, an age is calculated from the imputed birth date. In the case of dead siblings,
if either age at death or year of death is reported, that information is combined with the birth date to produce
missing information. If both pieces of information are missing, the age at death is imputed. This imputation is
based on the distribution of the ages at death for those whose year of death is unreported, but age at death is
reported.
108 * Adult and Maternal Mortality