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Informational Herding and Optimal Experimentation

Author

Listed:
  • Lones Smith

    (Dept. of Economics, University of Michigan)

  • Peter Norman Sorensen

    (Department of Economics, University of Copenhagen)

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.

Suggested Citation

  • Lones Smith & Peter Norman Sorensen, 2006. "Informational Herding and Optimal Experimentation," Cowles Foundation Discussion Papers 1552, Cowles Foundation for Research in Economics, Yale University.
    • Handle: RePEc:cwl:cwldpp:1552
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    References listed on IDEAS

    as
    1. Philippe Aghion & Patrick Bolton & Christopher Harris & Bruno Jullien, 1991. "Optimal Learning by Experimentation," The Review of Economic Studies, Review of Economic Studies Ltd, vol. 58(4), pages 621-654.
    2. Matthew Doyle, 2010. "Informational externalities, strategic delay, and optimal investment subsidies," Canadian Journal of Economics, Canadian Economics Association, vol. 43(3), pages 941-966, August.
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    13. Burdett, Kenneth, 1996. "Truncated means and variances," Economics Letters, Elsevier, vol. 52(3), pages 263-267, September.
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    Cited by:

    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.
    2. Matthew Doyle, 2010. "Informational externalities, strategic delay, and optimal investment subsidies," Canadian Journal of Economics, Canadian Economics Association, vol. 43(3), pages 941-966, August.
    3. S. Ali & Navin Kartik, 2012. "Herding with collective preferences," Economic Theory, Springer;Society for the Advancement of Economic Theory (SAET), vol. 51(3), pages 601-626, November.
    4. Alessandro Lizzeri & Marciano Siniscalchi, 2008. "Parental Guidance and Supervised Learning," The Quarterly Journal of Economics, President and Fellows of Harvard College, vol. 123(3), pages 1161-1195.
    5. Gleason, Kimberly C. & Mathur, Ike & Peterson, Mark A., 2004. "Analysis of intraday herding behavior among the sector ETFs," Journal of Empirical Finance, Elsevier, vol. 11(5), pages 681-694, December.
    6. Jacob K. Goeree & Thomas R. Palfrey & Brian W. Rogers & Richard D. McKelvey, 2007. "Self-Correcting Information Cascades," The Review of Economic Studies, Review of Economic Studies Ltd, vol. 74(3), pages 733-762.
    7. Christos Koulovatianos & Leonard J. Mirman & Marc Santugini, 2006. "Investment in a Monopoly with Bayesian Learning," Vienna Economics Papers vie0603, University of Vienna, Department of Economics.

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    More about this item

    Keywords

    Bayesian learning; value function; herding; experimentation; log concavity; Gittins index; team equilibrium;
    All these keywords.

    JEL classification:

    • D83 - Microeconomics - - Information, Knowledge, and Uncertainty - - - Search; Learning; Information and Knowledge; Communication; Belief; Unawareness

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