Requisition or labor time ticket to indicate the amount of overhead that enters into of Costs t. Yet overhead is as much a part of product's manufacturing cost as dir a nd direct labor. Because automation has increased, overhead has become a larger percentage of total product cost, while direct labor's percentage has declined. second characteristic of overhead deals with how different items of in response to a change in production volume. Overhead can be fixed variable. As discussed in Chapter 3, fixed overhead remains relatively less of changes in the level of output, within the relevant range, another that relationship is that fixed overhead per unit of output varies inversely with production volume. Variable overhead changes proportionately with production the relevant range: in other words. variable overhead per unit of output is constant. Semi Variable overhead is neither fixed nor variable: its amount changes, but not in production volume. As volume changes, the different overhead cost cause per-unit manufacturing cost to fluctuate considerably. As a result,some method is needed to determine an amount of overhead charged to the units produced