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). In these fields 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' ihas low reability. This affect the reliability oflevel and trend for this group (*50&am