A Appendix
A.1 Estimation of net intake ratios
This appendix describes how enrolment figures are used to estimate net intake ratios
and educational attainment. The main problem with estimating intake ratios is
accounting for students that have dropped out and thus that do not appear in the
enrolment figures. Neglecting dropouts leads to underestimations of the actual intake
rates and thus the educational attainment of the population. This is not an important
source of bias for most of the OECD countries because dropout rates there are relatively
low. But developing countries, and especially low-income countries, display
dropout rates as high as 15%. Another source of bias is the presence of repeaters in
the enrolment data, which leads to overestimations of the number of students that
have received formal education. Although existing measures of educational attainment
generally adjust their estimates by the repeater effect, they fail to take into
account the dropout effect.