Because of pressure from a concept of analytical necessity, account data must be reported for comparable periods of time. This is so because accounting is committed, by its reporting function, to hold its data as closely as is reasonably possible within realistic classification boundaries. The entity is the most prominent of these categories, but the fiscal year is another prominent category. With these two categories in mind, account figures speak with authority of transactions where the output price of the seller and the input price of the buyer are identical. Only by review of his account data can either party review in retrospect his prior valuation judgment.