Tractable Consumer Choice

We derive a rational model of separable consumer choice which can also serve as a behavioral model. The central construct is lambda, the marginal utility of money, derived from the consumer's rest-of-life problem. We present a robust approximation of lambda, and show how to incorporate liquidity constraints, indivisibilities and adaptation to a changing environment. We find connections with numerous historical and recent constructs, both behavioral and neoclassical, and draw contrasts with standard partial equilibrium analysis. The result is a better grounded, more flexible and more intuitive description