In order to ensure that prices established are representative of national production, it is necessary to make price-reporting compulsory in relation to slaughterhouses which slaughter, or persons who send for slaughter, substantial numbers of adult bovine animals, so as to ensure that at least 25 % of slaughterings in the main production regions and at least 30 % of slaughterings in each Member State are covered, and to weight the prices reported from different regions in order to reflect their importance in relation to beef and veal production.