Identifying the cost-allocation bases defines the number of activity pools into witch costs must be
grouped in an ABC system. For example, rather than define the design activities of product design, and prototyping as separate activities, Plastim's managers define these three activities together as a combined
“design” activity and form a homogeneous design cost pool. Why? Because the same cost driver-the complexity of the mold-drives the cost of each design activity. A second consideration for choosing a cost-allocation base is the availability of reliable data and measures. For example, in its ABC system, Plastim's managers measure mold complexity in terms of the number of parts in the mold and the surface area of the mold (part-square feet). If these data are difficult to obtain or measure, Plastim's managers may be forced to use some other measure of complexity, such as the amount of material flowing through the mold that may only be weakly related to the cost of the design activity