The exam results are taken from the register with pupil and final exam results in secondary education for school year 2005/'06. The register lists all exam subjects of individual pupils with their marks for the school components, the national paper and the final result. The final mark for a subject consisting of both a school component and a national component is derived by averaging them and rounding tem off to a whole number (maximum score is 10).
The average difference between the school and the national component is calculated by - for each individual pupil - taking the subjects for which the two components are included in the resister. Subjects on the list of final exam results which do not have a national component (physical education) are therefore not included.