In sum, the information needs of managers range from simple to complex, and
depend on the nature of products and processes, the particular decision to be made, the
competitive environment, and other factors. In contrast, the nature of inventory costing
required in external reporting is constant through time unless an external reporting rule
is changed. In addition, inventory costing must satisfy only the following: (1) it must be
based on actual historical costs, verifiable through documented transactions; (2) it must
be consistent from period to period; and (3) it must include all manufacturing costs in the
cost calculated for each unit of output.