Combining Labor and Factory Overhead Costs. The preceding illustration shows direct labor being charged separately to each department by means of a general journal entry. Increasing levels of automation cause direct labor to be a decreasing proportion of total manufacturing cost. Furthermore, in highly automated factories the distinction between the tasks performed by direct and indirect labor is often blurred. Also, factory overhead costs such as equipment depreciation, power, and maintenance tend to increase with automation. As a result, some manufacturers combine the labor and factory overhead cost elements and refer to them as conversion cost or simply as factory overhead. Direct labor is then not charged separately; instead, a single amount of applied conversion cost is charged to each department.