In the system of vocational training run by the chambers of industry and commerce, more than 150,000 volunteer examiners sit on more than 30,000 examination boards. They come from working life, and every year they hold more than 600,000 interim and final examinations. A principle of the system is Wer lehrt, prüft nicht, the person who teaches does not examine. These figures are from 2018 and cover only the chambers of industry and commerce, not the chambers of crafts.