The Revco method of amortization is not acceptable. If an imputed interest rate is suitable for determining asset amounts indirectly through the determination of expense, it is suitable for measuring assets as independent values. The traditional annuity method of depreciation makes appropriate use of an imputed interest rate in the measurement of assets. Before adopting the annuity method, however, one must be fully aware that its use with an imputed interest rate involves the acceptance of the corresponding set of future service values. The asset value under the annuity method of amortization is the discounted value of an assumed set of future service flows. This means that the use of the annuity method of depreciation involves a reliance on future service flows rather than historical cost for asset measurement. The cost based amortization method that yields asset values conceptually nearest to those of the annuity method with an imputed interest rate is the annuity method with an actual interest cost rate, or estimated future interest cost rate. If there is no interest cost, one cannot use it in accounting for the cost of assets. If there is an interest cost of holding assets, the total of it and the other costs should be spread evenly over the units of service received.