Oxford Economic Papers Advance Access originally published online on August 26, 2005
Oxford Economic Papers 2005 57(4):586-609; doi:10.1093/oep/gpi025
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© Oxford University Press 2005; All rights reserved
Diminishing marginal value of income without apology
Department of Economics, Albers School of Business and Economics, Seattle University, 901 12th Avenue, P.O. Box 222000, Seattle, WA 981221090, USA; e-mail: cweber{at}seattleu.edu
This paper considers value functions for maximization problems where the objective function is maximized subject to several constraints. I show that such value functions exhibit diminishing marginal rates of substitution (MRS) between the resource endowments which define the constraints. For the household, this implies that an ordinally defined marginal value of income falls as income rises. I also derive conditions under which the value function is homothetic in the endowments, so that the MRS between two resources is a monotone function of the ratio of the endowments of those resources and under which the MRS between two resources declines when one resource is increased with the other held constant, i.e., under which the marginal rate of substitution declines when the households moves from one indirect indifference curve to another. I apply these results to a model with two linear constraints and to a model of asset choice under uncertainty.
Key Words: JEL classification: D11 C61 D81