In most cases school year is used as referenceperiod. This means, that only information for the period uptill August is included when the calculation is based on the latest calender year . There is a slight difference between NYT (Highschools) from the 27. Feb. 2012 and tables based on the Statbank. For documentation follow this link (in danish): http://www.dst.dk/ext/uddannelse/Uddannelsestabeller.