1. Market price valuation applied in national accounts; 2. Value of natural resources and of their depletion and degradation, imputed in environmental accounting and estimated on the basis of expected market returns. Methods applied, in the absence of market prices of natural assets, include (a) the net present value of future net returns from natural asset use, (b) the net price method which determines the unit asset value as the difference between market price of a raw material minus its unit exploitation cost (including a normal return to the produced capital invested) and (c) the user cost allowance, i.e. the difference between the finite net returns from the sales of an exhaustible asset during the accounting period and "true" income remaining after investing the allowance during the lifetime of the asset so as to penetrate a permanent income stream. See also discounting (of natural assets) and Hotelling rent.