An activity may be incorporated in different production processes for making different products or services. To trace the activity costs to products an activity driver is required. The activity driver is a variable that reflects the frequency and intensity of the demands placed on
activities by the product or service. For example, different products will be sold in different volumes, so the number of products per order may be a good basis to assign the costs of order processing to each of the products. These concepts and relations constitute the theory of ABC. In summary, the cost of a resource per product is derived from the level of demand placed on
the activity (that consumes the resource) by the product represented by the activity driver measure--and the level of consumption of the specific resource by the activity--represented by the resource driver measure