Near that extreme are the costs that can be empirically traced to the unit’s production by observing the production process. These include: the labor expended to convert raw materials into finished product and some material-handling labor; paper patterns and other materials that are consumed in the production of each unit but are not physically incorporated into it; and some energy costs. Of course, not all items that are physically or empirically traceable to a unit will be important enough to justify the effort required to trace and record them. Whether tracing is justified depends on how precise a measure of direct costs is needed and how difficult or costly the tracing will be, For that reason, cost accounting systems generally treat as direct costs only some of the cost items that conceivably could be traced directly to the product unit