An Intertemporal Model of Saving and Investment
The standard model of optimal growth, interpreted as a model of a market economy with infinitely long-lived agents, does not allow separation of the savings decisions of agents from the investment decisions of firms. Investment is essentially passive: the "one good" assumption leads to a perfectly elastic investment supply; the absence of installation costs for investment leads to a perfectly elastic investment demand. On the other hand, the standard model of temporary equilibrium used in macroeconomics characterizes both the savings-consumption decision and the investment decision, or, equivalently, derives a well-behaved aggregate demand which, in equilibrium, must be equal to aggregate supply. Often, however, we want to study the movement of the temporary equilibrium over time in response to a particular shock or policy. The discrepancy between the treatment of investment in the two models makes imbedding the temporary equilibrium model in the growth model difficult. This paper characterizes the dynamic behavior of the optimal growth model with adjustment costs. It shows the similarity between the temporary equilibrium of the corresponding market economy and the short-run equilibrium of standard macroeconomic models: consumption depends on wealth, investment on Tobin's q. Equilibrium is maintained by the endogenous adjustment of the term structure of interest rates. It then shows how the equivalence can be used to study the dynamic effects of policies; it considers various fiscal policies and exploits their equivalence to technological shifts in the optimal growth problem.
|Date of creation:||Apr 1982|
|Date of revision:|
|Publication status:||published as Abel, Andrew B., & Oliver J. Blanchard. "An Intertemporal Model of Saving and Investment." Econometrica, Vol. 51, No. 3, (May 1983), pp. 675-692.|
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- Martin L. Weitzman, 1973. "Duality Theory for Infinite Horizon Convex Models," Management Science, INFORMS, vol. 19(7), pages 783-789, March.
- Hall, Robert E, 1971. "The Dynamic Effects of Fiscal Policy in an Economy With Foresight," Review of Economic Studies, Wiley Blackwell, vol. 38(114), pages 229-44, April.
- Kemp, Murray C & Long, Ngo Van, 1977. "Optimal Control Problems with Integrands Discontinuous with Respect to Time," The Economic Record, The Economic Society of Australia, vol. 53(142&143), pages 405-20, June-Sept.
- James Tobin, 1977. "Monetary Policies and the Economy -- The Transmission Mechanism," Cowles Foundation Discussion Papers 456, Cowles Foundation for Research in Economics, Yale University.
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