Education, Employment and Earnings of Secondary School-Leavers ...

It should be noted, however, that estimating earnings equations using tracer surveydata provides limited information on the age-earnings profile since in such surveysindividuals tend to be clustered around certain ages determined by school starting ageand individual progression through the school system. In addition, tracer surveys onlyinclude information on a cohort of individuals that has achieved a certain level ofeducation and/or training and therefore contains no information on those who havelower levels of education or no formal education. For example, the focus of the tracersurveys in this study is on secondary education. Therefore, all individuals in theanalysis have attained at least junior secondary education.Another potential drawback of tracer surveys is that they suffer from sample selectionissues that potentially bias the analysis towards individuals that are more easilytraced. For example, some tracer surveys do not sample individuals from a completelist (sample frame) of individuals with the same training. Instead they traceindividuals by visiting major enterprises or organisations where individuals with thespecified training are likely to work. All those that were not able to get work in theseorganisations are excluded, potentially biasing any analysis of the group as a whole.In cases where tracer surveys do use a sample frame to randomly select individualsthey only manage to trace a small proportion of the sampled individuals. Again, lowresponse rates may be taken to infer that selection bias is likely to be a seriousproblem.The tracer survey for this study was carefully designed to avoid the type of problemscommonly associated with surveys of this kind. The tracer survey aimed to locate aspecific group of secondary school-leavers that completed the first four years ofsecondary schooling in Tanzania. The sample of secondary school-leavers wasselected from ten average performing secondary schools: five located in Dar esSalaam and five in Dodoma. 10 The sample frame consisted of all students in theseschools who completed their junior secondary schooling in 1990 or 1995. A random10 As mentioned in the previous section secondary school access was very low during the 1990s and the10 sampled schools represents about 2 per cent of the total number of secondary schools in Tanzania atthis time.8