In most cases school year is used as referenceperiod., i.e. only information for the period uptill August is included when the calculation is based on the latest calender year. Except for the main groups 35 and 40 (field of education). Here the whole calender year is covered also for the last year.Due to defective reports from one school the number of full HD-education in the group;50 has low reability. Note that socioeconomic status has not been updated.