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Different theories of expectation formation and learning usually yield different outcomes for realized market prices in dynamic models. The purpose of this paper is to investigate expectation formation and learning in a controlled experimental environment. Subjects are asked to predict the next period's aggregate price in a dynamic commodity market model with feedback from individual expectations. Subjects have no information about underlying market equilibrium equations, but can learn by observing past price realizations and predictions. We conduct a stable, an unstable, and a strongly unstable treatment. In the stable treatment, rational expectations (RE) yield a good description of observed aggregate price fluctuations: prices remain close to the RE steady state. In the unstable treatments, prices exhibit large fluctuations around the RE steady state. Although the sample mean of realized prices is close to the RE steady state, the amplitude of the price fluctuations as measured by the variance is significantly larger than the amplitude under RE, implying persistent excess volatility. However, agents' forecasts are boundedly rational in the sense that fluctuations in aggregate prices are unpredictable and exhibit no forecastable structure that could easily be exploited.

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Address correspondence to: Cars Hommes, Center for Nonlinear Dynamics in Economics and Finance (CeNDEF), University of Amsterdam, Roetersstraat 11, NL-1018 WB Amsterdam, The Netherlands; e-mail:
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Arifovic J. 1994 Genetic algorithm learning and the cobweb model. Journal of Economic Dynamics and Control 18, 328.
Bray M.M. and N.E. Savin 1986 Rational expectations equilibria, learning and model specification. Econometrica 54, 11291160.
Brock W.A. and C.H. Hommes 1997 A rational route to randomness. Econometrica 65, 10591095.
Carlson J. 1967 The stability of an experimental market with a supply response lag. Southern Economic Journal 33, 305321.
Chiarella C. 1988 The cobweb model: Its instability and the onset of chaos. Economic Modelling 5, 377384.
Evans G.W. and S. Honkapohja 1999 Learning dynamics. In J.B. Taylor and M. Woodford (eds.), Handbook of Macroeconomics, Vol. 1A, pp. 449542. Amsterdam: Elsevier.
Evans, G.W. and S. Honkapohja 2001 Learning and Expectations in Macroeconomics. Princeton, NJ: Princeton University Press.
Ezekiel M. 1938 The cobweb theorem. Quarterly Journal of Economics 52, 255280.
Frankel J.A. and K.A. Froot 1987 Using survey data to test standard propositions regarding exchange rate expectations. American Economic Review 77, 133153.
Grandmont J.M. 1998 Expectations formation and stability in large socio-economic systems. Econometrica 66, 741781.
Grandmont, J.M. and G. Laroque 1991 Economic dynamics with learning: some instability examples. In W.A. Barnett, B. Cornet, C. d'Aspremont, J. Gabszewicz and A. Mas-Colell (eds.), Equilibrium Theory and Applications, pp. 247273. Cambridge: Cambridge University Press.
Guesnerie R. 1992 An exploration of the eductive justifications of the rational expectations hypothesis. American Economic Review 82, 12541278.
Guesnerie R. 2002 Anchoring economic predictions in common knowledge. Econometrica 70, 439480.
Hey J.D. 1994 Expectations formation: rational or adaptive or…? Journal of Economic Behavior and Organization 25, 329349.
Holt C.A. and A.P. Villamil 1986 A laboratory experiment with a single person cobweb. Atlantic Economic Journal 14, 5154.
Hommes C.H. 1994 Dynamics of the cobweb model with adaptive expectations and nonlinear supply and demand. Journal of Economic Behavior and Organization 24, 315335.
Hommes C.H., J. Sonnemans, J. Tuinstra, and H. van de Velden 2005 Coordination of expectations in asset pricing experiments. Review of Financial Studies 18, 955980.
Hommes C.H., J. Sonnemans and H. van de Velden 2000 Expectation formation in an experimental cobweb economy. In D. Delli Gatti, M. Gallegati and A. Kirman (eds.). Interaction and Market Structure: Essays on Heterogeneity in Economics. Lecture Notes in Economics and Mathematical Systems, volume 484, pp. 253266. Berlin: Springer-Verlag.
Hommes C.H. and G. Sorger 1998 Consistent expectations equilibria. Macroeconomic Dynamics 2, 287321.
Kelley H. and D. Friedman 2002 Learning to forecast price. Economic Inquiry 40, 556573.
Lucas, R.E. 1972 Econometric testing of the natural rate hypothesis. In O. Eckstein (ed.). The Econometrics of Price Determination Conference, pp. 5059. Board of Governors of the Federal Reserve System and Social Science Research Council, Washington, DC.
Marimon R. 1997 Learning from learning in economics. In D.M. Kreps and K.F. Wallis (eds.). Advances in Economics and Econometrics: Theory and Applications, Seventh World Congress of the Econometric Society, Volume I, pp. 278315. Cambridge: Cambridge University Press.
Marimon, R., S.E. Spear and S. Sunder 1993 Expectationally driven market volatility: an experimental study. Journal of Economic Theory 61, 74103.
Marimon R. and S.E. Sunder 1993 Indeterminacy of equilibria in a hyperinflationary world: experimental evidence. Econometrica 61, 10731108.
Muth J.F. 1961 Rational expectations and the theory of price movements. Econometrica 29, 315335.
Nerlove M. 1958 Adaptive expectations and cobweb phenomena. Quarterly Journal of Economics 72, 227240.
Sargent T.J. 1993 Bounded Rationality in Macroeconomics. Oxford: Clarendon Press.
Sargent T.J. 1999 The Conquest of American Inflation. Princeton, NJ: Princeton University Press.
Shiller R.J. 1981 Do stock prices move to much to be justified by subsequent changes in dividends? American Economic Review 71, 421436.
Shiller R.J. 1989 Market Volatility. Cambridge, MA: MIT Press.
Shiller R.J. 2000 Measuring bubble expectations and investor confidence. Journal of Psychology and Financial Markets 1, 4960.
Smith V.L., G.L. Suchanek and A.W. Williams 1988 Bubbles, crashes and endogenous expectations in experimental spot asset markets. Econometrica 56, 11191151.
Sunder S. 1995 Experimental asset markets: a survey. In J. Kagel and A. Roth (eds.). Handbook of Experimental Economics, pp. 445500. Princeton, NJ: Princeton University Press.
van de Velden H. 2001 An Experimental Approach to Expectation Formation in Dynamic Economic Systems. Ph.D. thesis, Tinbergen Institute, University of Amsterdam.
Wellford C.P. 1989 A Laboratory Analysis of Price Dynamics and Expectations in the Cobweb Model. Discussion Paper No. 89-15, Department of Economics, University of Arizona.
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Macroeconomic Dynamics
  • ISSN: 1365-1005
  • EISSN: 1469-8056
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