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Shills and Shipes

Author

Listed:
  • Subir Bose

    ()

  • Arup Daripa

    ()

Abstract

Online auctions with a fixed end-time often experience a sharp increase in bidding towards the end despite using a proxy-bidding format. We provide a novel explanation of this phenomenon under private values. We study a correlated private values environment in which the seller bids in her own auction (shill bidding). Bidders selected randomly from some large set arrive randomly in an auction, then decide when to bid (possibly multiple times) over a continuous time interval. A submitted bid arrives over a continuous time interval according to some stochastic distribution. The auction is a continuous-time game where the set of players is not commonly known, a natural setting for online auctions. Our results are robust with respect to the seller’s and the bidders’ priors regarding the set of bidders arriving at the auction. We show that there is a late-bidding equilibrium in which bids are delayed to the latest instance involving no sacrifice of probability of bid arrival, but shill bids fail to arrive with positive probability, and in this sense optimal late bidding serves to snipe the shill bids. We show conditions under which the equilibrium outcome is unique. Further, if these conditions do not hold, and there are any equilibria with a different outcome, they are necessarily characterized by early bidding. Any such equilibria are Pareto dominated for the bidders compared to the late-bidding equilibrium. Finally, our results suggest that under private values, the case against shill-bidding might be weak.

Suggested Citation

  • Subir Bose & Arup Daripa, 2014. "Shills and Shipes," Discussion Papers in Economics 14/12, Division of Economics, School of Business, University of Leicester.
  • Handle: RePEc:lec:leecon:14/12
    as

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    File URL: https://www.le.ac.uk/economics/research/RePEc/lec/leecon/dp14-12.pdf
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    References listed on IDEAS

    as
    1. Lamy, Laurent, 2009. "The Shill Bidding Effect versus the Linkage Principle," Journal of Economic Theory, Elsevier, vol. 144(1), pages 390-413, January.
    2. Indranil Chakraborty & Georgia Kosmopoulou, 2004. "Auctions with shill bidding," Economic Theory, Springer;Society for the Advancement of Economic Theory (SAET), vol. 24(2), pages 271-287, August.
    3. Alvin E. Roth & Axel Ockenfels, 2002. "Last-Minute Bidding and the Rules for Ending Second-Price Auctions: Evidence from eBay and Amazon Auctions on the Internet," American Economic Review, American Economic Association, vol. 92(4), pages 1093-1103, September.
    4. Engelberg, Joseph & Williams, Jared, 2009. "eBay's proxy bidding: A license to shill," Journal of Economic Behavior & Organization, Elsevier, vol. 72(1), pages 509-526, October.
    5. Ladislav Wintr, 2008. "Some Evidence On Late Bidding In Ebay Auctions," Economic Inquiry, Western Economic Association International, vol. 46(3), pages 369-379, July.
    6. Bajari, Patrick & Hortacsu, Ali, 2003. " The Winner's Curse, Reserve Prices, and Endogenous Entry: Empirical Insights from eBay Auctions," RAND Journal of Economics, The RAND Corporation, vol. 34(2), pages 329-355, Summer.
    7. Ockenfels, Axel & Roth, Alvin E., 2006. "Late and multiple bidding in second price Internet auctions: Theory and evidence concerning different rules for ending an auction," Games and Economic Behavior, Elsevier, vol. 55(2), pages 297-320, May.
    8. Kosmopoulou, Georgia & De Silva, Dakshina G., 2007. "The effect of shill bidding upon prices: Experimental evidence," International Journal of Industrial Organization, Elsevier, vol. 25(2), pages 291-313, April.
    9. Rasmusen Eric Bennett, 2006. "Strategic Implications of Uncertainty over One's Own Private Value in Auctions," The B.E. Journal of Theoretical Economics, De Gruyter, vol. 6(1), pages 1-22, November.
    10. Roger B. Myerson, 1981. "Optimal Auction Design," Mathematics of Operations Research, INFORMS, vol. 6(1), pages 58-73, February.
    11. Graham, Daniel A. & Marshall, Robert C. & Richard, Jean-Francois, 1990. "Phantom bidding against heterogeneous bidders," Economics Letters, Elsevier, vol. 32(1), pages 13-17, January.
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    More about this item

    Keywords

    Online auctions; correlated private values; last-minute bidding; sniping; shill bidding; random bidder arrival; continuous bid time; continuous bid arrival process.;

    JEL classification:

    • D44 - Microeconomics - - Market Structure, Pricing, and Design - - - Auctions

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