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Informational Herding and Optimal Experimentation

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Author Info
Lones Smith (Dept. of Economics, University of Michigan)
Peter Norman Sorensen () (Department of Economics, University of Copenhagen)

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Abstract

We show that far from capturing a formally new phenomenon, informational herding is really a special case of single-person experimentation -- and 'bad herds' the typical failure of complete learning. We then analyze the analogous team equilibrium, where individuals maximize the present discounted welfare of posterity. To do so, we generalize Gittins indices to our non-bandit learning problem, and thereby characterize when contrarian behaviour arises: (i) While herds are still constrained efficient, they arise for a strictly smaller belief set. (ii) A log-concave log-likelihood ratio density robustly ensures that individuals should lean more against their myopic preference for an action the more popular it becomes.

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File URL: http://cowles.econ.yale.edu/P/cd/d15b/d1552.pdf
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Publisher Info
Paper provided by Cowles Foundation, Yale University in its series Cowles Foundation Discussion Papers with number 1552.

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Length: 39 pages
Date of creation: Jan 2006
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Handle: RePEc:cwl:cwldpp:1552

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Related research
Keywords: Bayesian learning; value function; herding; experimentation; log concavity; Gittins index; team equilibrium;

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Find related papers by JEL classification:
D83 - Microeconomics - - Information, Knowledge, and Uncertainty - - - Search, Learning, and Information

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References listed on IDEAS
Please report citation or reference errors to , or , if you are the registered author of the cited work, log in to your RePEc Author Service profile, click on "citations" and make appropriate adjustments.:
  1. Sgroi, Daniel, 2002. "Optimizing Information in the Herd: Guinea Pigs, Profits, and Welfare," Games and Economic Behavior, Elsevier, vol. 39(1), pages 137-166, April. [Downloadable!] (restricted)
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  2. Chamley, Christophe & Gale, Douglas, 1994. "Information Revelation and Strategic Delay in a Model of Investment," Econometrica, Econometric Society, vol. 62(5), pages 1065-85, September. [Downloadable!] (restricted)
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  3. Bikhchandani, Sushil & Hirshleifer, David & Welch, Ivo, 1992. "A Theory of Fads, Fashion, Custom, and Cultural Change in Informational Cascades," Journal of Political Economy, University of Chicago Press, vol. 100(5), pages 992-1026, October. [Downloadable!] (restricted)
  4. Burdett, Kenneth, 1996. "Truncated means and variances," Economics Letters, Elsevier, vol. 52(3), pages 263-267, September. [Downloadable!] (restricted)
  5. Doyle, Matthew, 2002. "Informational Externalities, Strategic Delay, and the Search for Optimal Policy," Staff General Research Papers 10046, Iowa State University, Department of Economics. [Downloadable!]
  6. Banerjee, Abhijit V, 1992. "A Simple Model of Herd Behavior," The Quarterly Journal of Economics, MIT Press, vol. 107(3), pages 797-817, August. [Downloadable!] (restricted)
  7. Rothschild, Michael, 1974. "A two-armed bandit theory of market pricing," Journal of Economic Theory, Elsevier, vol. 9(2), pages 185-202, October. [Downloadable!] (restricted)
  8. Aghion Philippe & Bolton, Patrick & Harris Christopher & Jullien Bruno, 1991. "Optimal learning by experimentation," CEPREMAP Working Papers (Couverture Orange) 9104, CEPREMAP.
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  9. Lones Smith & Peter Sorensen, 2000. "Pathological Outcomes of Observational Learning," Econometrica, Econometric Society, vol. 68(2), pages 371-398, March.
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  10. McLennan, Andrew, 1984. "Price dispersion and incomplete learning in the long run," Journal of Economic Dynamics and Control, Elsevier, vol. 7(3), pages 331-347, September. [Downloadable!] (restricted)
  11. Vives, Xavier, 1993. "How Fast Do Rational Agents Learn?," Review of Economic Studies, Blackwell Publishing, vol. 60(2), pages 329-47, April. [Downloadable!] (restricted)
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  12. Dow, James, 1991. "Search Decisions with Limited Memory," Review of Economic Studies, Blackwell Publishing, vol. 58(1), pages 1-14, January. [Downloadable!] (restricted)
  13. Amir, Rabah, 1996. "Sensitivity analysis of multisector optimal economic dynamics," Journal of Mathematical Economics, Elsevier, vol. 25(1), pages 123-141. [Downloadable!] (restricted)
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  14. Aghion, Philippe, et al, 1991. "Optimal Learning by Experimentation," Review of Economic Studies, Blackwell Publishing, vol. 58(4), pages 621-54, July. [Downloadable!] (restricted)
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Cited by:
(explanations, Please report citation or reference errors to , or , if you are the registered author of the cited work, log in to your RePEc Author Service profile, click on "citations" and make appropriate adjustments.)

  1. Christos Koulovatianos & Leonard J. Mirman & Marc Santugini, 2006. "Investment in a Monopoly with Bayesian Learning," Vienna Economics Papers 0603, University of Vienna, Department of Economics. [Downloadable!]
  2. Jacob K. Goeree & Thomas R. Palfrey & Brian W. Rogers & Richard D. McKelvey, 2006. "Self-Correcting Information Cascades," Levine's Bibliography 321307000000000211, UCLA Department of Economics. [Downloadable!]
    Other versions:
  3. Doyle, Matthew, 2002. "Informational Externalities, Strategic Delay, and the Search for Optimal Policy," Staff General Research Papers 10046, Iowa State University, Department of Economics. [Downloadable!]
  4. Alessandro Lizzeri & Marciano Siniscalchi, 2006. "Parental Guidance and Supervised Learning," Discussion Papers 1432, Northwestern University, Center for Mathematical Studies in Economics and Management Science. [Downloadable!]
    Other versions:
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