Rate of out of school children, national source (% of relevant age group)
The national data used in the calculation of the out-of-school rate (OOSR) are based on enrolment at a specific date, which can over- or underestimate the results by either counting enrolled children who never attend school or by omitting those who enroll after the reference date for reporting enrolment data. Furthermore, children who drop out of school after the reference date are not counted as out of school children. Discrepancies between enrolment and population data from different sources can also result in over- or underestimates of the OOSR. The data derived from national sources may differ from international sources because of divergences in definitions, methods of calculation, or in some cases due to different underlying data.  For these reasons, the data based on national sources in this database should not be used for making comparisons between countries, but rather for assessing the progress of individual countries.
Number of children of official primary school age who are not enrolled in primary or secondary school, expressed as a percentage of the population of official primary school age. This indicator is intended to measure the size of the population in the official primary school age range that should be targeted by policies and efforts to achieve universal primary education. Country-specific definition, method and targets are determined by countries themselves.