Resources and Output Measures
Every activity needs resources to accomplish the task it has to do. Resources might include materials, energy or fuel, labor, and capital. These inputs are combined to produce an output. For example, if the activity is moving materials, the inputs could include Crates (materials), fuel (energy), a forklift operator (labor), and a forklift (capital). The output would be moved materials. But how do we measure this output? One measure is the number of times the activity is performed. For example, suppose that the activity is moving materials from the storeroom to the assembly line. A good measure of output is the number of moves. The more moves that are made, the higher the cost of moving. Therefore, we could say that the number of moves is a good output measure for the activity of moving materials. Exhibit 3-4 illustrates the relationship between inputs, activities, output, and cost behavior.
Another term for output measure is driver. Recall from Chapter 2 that activity drivers are observable causal factors that measure the amount of resources a cost object uses. Activity drivers explain changes in activity costs by measuring changes in activity use or output. Thus, the driver for material handling may be number of moves; the driver for shipping goods may be the units sold; and the driver for laundering hospital bedding may be pounds of laundry. The choice of driver is tailored not only to the particular firm but also to the particular activity or cost being measured. Therefore, in order to understand the behavior of costs, we must first determine the underlying activities and the associated drivers that measure activity capacity and usage. The need to understand this cost-activity relationship leads us to the determination of an appropriate measure of activity output, or activity driver.