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Informational Herding and Optimal Experimentation

Author

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  • Lones Smith

    (Department of Economics, University of Michigan)

  • Peter Norman Sørensen

    (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 Sørensen, 2005. "Informational Herding and Optimal Experimentation," Discussion Papers 05-13, University of Copenhagen. Department of Economics.
  • Handle: RePEc:kud:kuiedp:0513
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    File URL: http://www.econ.ku.dk/english/research/publications/wp/2005/0513.pdf/
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    References listed on IDEAS

    as
    1. Philippe Aghion & Patrick Bolton & Christopher Harris & Bruno Jullien, 1991. "Optimal Learning by Experimentation," Review of Economic Studies, Oxford University Press, vol. 58(4), pages 621-654.
    2. James Dow, 1991. "Search Decisions with Limited Memory," Review of Economic Studies, Oxford University Press, vol. 58(1), pages 1-14.
    3. 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.
    4. Rothschild, Michael, 1974. "A two-armed bandit theory of market pricing," Journal of Economic Theory, Elsevier, vol. 9(2), pages 185-202, October.
    5. Amir, Rabah, 1996. "Sensitivity analysis of multisector optimal economic dynamics," Journal of Mathematical Economics, Elsevier, vol. 25(1), pages 123-141.
    6. Xavier Vives, 1993. "How Fast do Rational Agents Learn?," Review of Economic Studies, Oxford University Press, vol. 60(2), pages 329-347.
    7. 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.
    8. Abhijit V. Banerjee, 1992. "A Simple Model of Herd Behavior," The Quarterly Journal of Economics, Oxford University Press, vol. 107(3), pages 797-817.
    9. Lones Smith & Peter Sorensen, 2000. "Pathological Outcomes of Observational Learning," Econometrica, Econometric Society, vol. 68(2), pages 371-398, March.
    10. Chamley, Christophe & Gale, Douglas, 1994. "Information Revelation and Strategic Delay in a Model of Investment," Econometrica, Econometric Society, vol. 62(5), pages 1065-1085, September.
    11. 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.
    12. 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.
    13. Burdett, Kenneth, 1996. "Truncated means and variances," Economics Letters, Elsevier, vol. 52(3), pages 263-267, September.
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    Citations

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    Cited by:

    1. 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.
    2. Alessandro Lizzeri & Marciano Siniscalchi, 2008. "Parental Guidance and Supervised Learning," The Quarterly Journal of Economics, Oxford University Press, vol. 123(3), pages 1161-1195.
    3. Jacob K. Goeree & Thomas R. Palfrey & Brian W. Rogers & Richard D. McKelvey, 2007. "Self-Correcting Information Cascades," Review of Economic Studies, Oxford University Press, vol. 74(3), pages 733-762.
    4. 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.
    5. 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.
    6. 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.

    More about this item

    Keywords

    herding; optimal learning; experimentation; contrarianism;

    JEL classification:

    • D82 - Microeconomics - - Information, Knowledge, and Uncertainty - - - Asymmetric and Private Information; Mechanism Design
    • D83 - Microeconomics - - Information, Knowledge, and Uncertainty - - - Search; Learning; Information and Knowledge; Communication; Belief; Unawareness

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