Classification of items in decreasing order of volume or sales. The items are normally split in three classes. Class A represents 10% to 20% of the number of items and 50% to 70% of volume. Class B represents 20% to 30% of the number of items and 20% to 30% of volume; Class C represents 50% to 70% of the number of items and 10% to 30% of volume.