Childhood Mortality EstimationThe infant mortality rate q(1) and under five mortality rate q(5) represent probabilities of dying before exact ages 1 and 5 years, respectively. Several indirect methods of measuring q(1) and q(5) have been suggested in the literature (UN, 1983). The data at our disposal do not permit the use of methods such as the preceding birth (PB) and life table methods. However, the Brass (1964) method and its variants are applicable in our case. We will arrive at estimates of q(1) and q(5) using two approaches. The first approach uses data on CEB and CS classified by age of mother. The second approach uses data on CEB and CS classified by duration of marriage. Once estimates are obtained, they will be compared with estimates of OT, made by UNICEF and JFPPA, and of neighbouring countries.
Estimates Using Data Classified by Age Group of Mothers
Table 2.6 Number of children ever born and children surviving by age group of mothers and sex of children
Further calculations show that the probability of dying before age x is almost identical for the two standard alternative procedures (Palloni-Heligman, Trussel). The only slight difference is in the estimated reference dates. However, the differences between the reference dates are not of a large magnitude. For trend assessment, estimates of q(1) and q(5) can be converted to common indices as shown in table 2.7 together with life expectancy at birth, e0.
Table 2.7 Estimates of probability of dying by exact age 1 an d 5 and life expectancy at birth (in common indices) using two different versions
Inspection of the estimates of q(1) and q(5) shows a clear mortality decline
during the last 15 years. The high estimate of q(x) for May 1990 is expected
since it is based on an age group (20-24) where many women marry and have
their first child, there is usually a surplus mortality for first births.
To get a single estimate for q(1), q(5) and e0, we use the weighted average of the estimates of each parameters for age groups 20-24 and 25-29. The weights suggested here are the proportion of CEB in each age group (0.336 for 20-24 and 0.664 for 25-29). This is done to avoid discarding the mortality experience for the 20-24 age group altogether, and to obtain estimates that are fairly recent.
Our estimate of q(1) is 43 deaths per one thousand live births for both the Palloni-Heligman and Trussell approaches. The Palloni-Heligman estimate refers to February 1989 and the Trussell's estimate refers to December 1988, both of which in practice refer to the same time period. The estimate of q(5) for the same reference dates is 56 deaths per one thousand live births. The two procedures also give very similar estimates of q(1) and q(5) for each sex.
We have also estimated child mortality using children ever born and children surviving by duration of marriage of mothers, using Trussell's procedure, see table 2.8.
Table 2.8 Estimates of probability of dying by exact age x, 1 and 5 and life expectancy at birth, Trussell version
Generally, estimates of q(x) based on data by duration of marriage are expected to be more reliable than those derived from data by age of mother, due to a higher accuracy in reporting age at first marriage (being a memorable experience). However, for this data set, the sample size is not large enough to permit reliable estimation. Therefore, since we are looking for trends in IMR and U5MR rather than specific point estimates, both approaches show a decline in q(1) and q(5) during the last fifteen years, but the decline based on the age-of-mother data is more systematic. Moreover, the decline in q(1) and q(5) resulting from the age group method agree quite well with that reported by UNICEF and JFPPA for the same period. Based on these arguments, we recommend adopting the q(x) values based on data by age of mother.