The New Palgrave Dictionary of Economics

2018 Edition
| Editors: Macmillan Publishers Ltd

Perfect Foresight

  • Margaret Bray
Reference work entry


Perfect foresight is an occasionally convenient theoretical assumption whose total lack of realism is undisputed, and perhaps unrivalled. There are two elements to perfect foresight; firstly that people have definite point expectations, allowing no uncertainty, of future variables, and secondly that these expectations are correct. In practice, as these fortunate perfectly foresightful individuals generally inhabit models with instantaneously clearing perfectly competitive markets, they only need to forecast prices. The pioneering work by Hicks (1939) on intertemporal general equilibrium theory provides a framework in which the issues associated with perfect foresight can be explored. Writing prior to the development of the expected utility theory of choice under uncertainty (von Neumann and Morgenstern 1944), Hicks had no alternative to a deterministic model in his discussion. He acknowledges the existence and importance of uncertainty in expectation formation, but argues in a somewhat unsatisfactory fashion that point predictions can be interpreted as risk-adjusted summaries of underlying probability distributions. Hicks divides time into weeks. Trade takes place weekly. Supply and demand in each week depend upon decisions made in the past, expectations of spot prices in future weeks, and current spot prices. In temporary equilibrium these spot prices adjust to clear markets, but expectations may be wrong. In the situation which Hicks terms ‘Equilibrium over Time’, markets clear at each date, and, crucially, everyone has perfect foresight; price expectations are fulfilled.


Cobweb model Expectations Imperfect information Intertemporal general equilibrium Overlapping generations models Perfect foresight Probability distribution Rational expectations equilibrium Stationary state Uncertainty 

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  1. Bliss, C.J. 1975. Capital theory and the distribution of income. Amsterdam: North- Holland.Google Scholar
  2. Bray, M.M. 1983. Convergence to rational expectations equilibrium. In Individual forecasting and aggregate outcomes, ed. R. Frydman and E.S. Phelps. Cambridge: Cambridge University Press.Google Scholar
  3. Debreu, G. 1959. Theory of value: An axiomatic analysis of economic equilibrium. Coules foundation monograph no. 17. New York: Wiley.Google Scholar
  4. Grandmont, J.-M. 1985. On endogenous competitive business cycles. Econometrica 53: 995–1045.CrossRefGoogle Scholar
  5. Hicks, J.R. 1939. Value and capital. Oxford: Clarendon Press.Google Scholar
  6. Kaldor, N. 1934. A classificatory note on the determinateness of equilibrium. Review of Economic Studies 1: 122–136.CrossRefGoogle Scholar
  7. Knight, F.H. 1921. Risk, uncertainty and profit. Boston: Houghton Mifflin.Google Scholar
  8. Muth, J.F. 1961. Rational expectations and the theory of price movements. Econometrica 29: 315–335.CrossRefGoogle Scholar
  9. von Neumann, J., and O. Morgenstern. 1944. Theory of games and economic behavior. Princeton: Princeton University Press.Google Scholar

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© Macmillan Publishers Ltd. 2018

Authors and Affiliations

  • Margaret Bray
    • 1
  1. 1.