Over the years, accounting theorists have debated the respective merits of alternative accounting measurement approaches. Those favoring historical cost base their argument on the premise that cost is objective and verifiable. Historical cost is not based on subjective estimations; rather, it is the result of the value buyers and sellers have agreed to in an “arm’s-length” transaction. Some accounting theorists have even suggested that historical cost actually represents the present values of expected future cash flows at the time the exchange takes places. It is also argued that accountants serve a stewardship role, and because cost measure the actual resources exchanged, it is relevant to readers of financial statements. Opponents of historical cost maintain that values many change over time and, consequently, that historical cost can lose its relevance as a valuation base.