An Activity Analysis Approach to Unit Costing with Multiple Interactive Products

Average variable costs are not directly defined for multiple products produced in complex production settings. An activity analysis model can be used for basic cost measurement and for building a linear programming model of manufacturing operations. The model can then be used not only to compute the optimal production plan and associated marginal costs but also to assign average costs to final products. The activity analysis framework enables many overhead costs, such as maintenance, overtime, shift premiums, and indirect labor and materials, to be treated within the model. Thus, they are absorbed directly into the cost of final products rather than allocated indirectly through an overhead charge. Three average costing methods based on sacrifice value (marginal costs) and benefit value (marginal revenue) of products are considered. The method based entirely on the market value of products has less desirable properties than allocation methods which use the dual variables (marginal costs) from the programming model. Another benefit is that various cost allocation methods using input-output analysis can be considered as special cases of average costing methods presented in this paper.