First, inventory cost measurement, in itself, is a tough problem. There are a number of alternative cost accounting systems that can be relevant for some purposes while being inadequate or dangerous for others (cf. Edward A. Silver, David F. Pyke and Rein Peterson, see below References n°4). Then, it is neither always possible nor economical to keep track of all costs, or to split them and allocate them properly. To start assessing inventory costs, one has to understand that the relevant numbers won’t always appear in conventional accounting records, and when it seems that they do, one still has to be careful about the set of rules and assumptions used to produce those numbers. For instance, at the time of combining the different costs, one needs to make sure that the elements are consistently expressed either as before-tax figures or after-tax and not a mix of the two.