An alternative approach used in the traditional system, is provided by Variable or
Marginal costing, which overcame the arbitrary nature of allocation in the case of fixed
costs. Such a system concentrates on variable manufacturing costs, which are assigned to
products and included in the inventory valuation. Marginal costing is a costing method
that includes only variable manufacturing costs – direct material, direct labour, and
variable manufacturing overhead – in the cost of a unit of product, where on the other
hand fixed overhead costs are assigned to the period in which they are incurred .
In fact, it is not possible for systems which use a single absorption/allocation base to
yield accurate cost information because no single factor can explain the variation and consumption of the total overheads. In the hope of achieving “reliable” allocation of manufacturing overheads, ABC emerged. ABC would seem to present an opportunity to provide a better decision-making base for managers.