Using data from hospitals in the state of Washington, we examine the time-series behavior of overhead costs. We find that more accurate predictions of changes in costs are usually generated by assuming a cost will not change at all (except for inflation) than by assuming that the cost will...

Costing systems including activity-based costing generate average cost data. When these average costs are used for decision-making it is implicitly assumed that they approximate marginal costs. (In other words it is assumed every cost is strictly proportional to activity they are entirely...