Avoiding ballot stuffing in eBay-like reputation systems

ABSTRACT

We present a preliminary study on the robustness of binary feedback reputation systems (e.g. eBay) to ballot stuffing and bad mouthing. In a feedback based reputation system, a seller can collude with other buyers to undertake fake transactions in order to enhance her reputation. This problem is referred to as ballot stuffing. A seller can also be targeted by a group of buyers to deliberately lower her reputation. This problem is referred to as bad mouthing. For the reputations to be meaningful, any practical reputation system needs to be resistant to these problems. We use a simplified model to give an explicit relation between the reputation premium and the transaction cost that needs to hold in order to avoid ballot stuffing. Thus we draw attention to the necessity of transaction costs for a well functioning reputation system. Our conclusions are confirmed by empirical experiments on eBay.

REFERENCES

• 1: S. Ba and P.A. Pavlou. Evidence of the effect of trust building technology in electronic markets: Price premiums and buyer behavior. MIS Quart., 26:243--268, 2002.
• 2: Gary E. Bolton , Elena Katok , Axel Ockenfels, How Effective Are Electronic Reputation Mechanisms? An Experimental Investigation, Management Science, v.50 n.11, p.1587-1602, November 2004 [doi>10.1287/mnsc.1030.0199]
• 3: Chrysanthos Dellarocas, Immunizing online reputation reporting systems against unfair ratings and discriminatory behavior, Proceedings of the 2nd ACM conference on Electronic commerce, p.150-157, October 17-20, 2000, Minneapolis, Minnesota, United States [doi>10.1145/352871.352889]
• 4: Chrysanthos Dellarocas, Mechanisms for coping with unfair ratings and discriminatory behavior in online reputation reporting systems, Proceedings of the twenty first international conference on Information systems, p.520-525, December 2000, Brisbane, Queensland, Australia
• 5: Chrysanthos Dellarocas, Analyzing the economic efficiency of eBay-like online reputation reporting mechanisms, Proceedings of the 3rd ACM conference on Electronic Commerce, p.171-179, October 14-17, 2001, Tampa, Florida, USA [doi>10.1145/501158.501177]
• 6: Chrysanthos Dellarocas, The Digitization of Word of Mouth: Promise and Challenges of Online Feedback Mechanisms, Management Science, v.49 n.10, p.1407-1424, October 2003 [doi>10.1287/mnsc.49.10.1407.17308]
• 7: E. Friedman and P. Resnick. The social cost of cheap pseudonyms. Journal of Economics and Management Strategy, 10(1):173--199, 2001.
• 8: GartnerG2. Online transaction fraud and prevention get more sophisticated. http://www.gartnerg2.com/rpt/rpt-0102-0013.asp. 2002.
• 9: D. Lucking-Reiley, D. Bryan, N. Prasad, and D. Reeves. Pennies from ebay: The determinants of price in online auctions. Working paper, Vanderbilt University, Nashville, TN, 1999.
• 10: M.I. Melnik and J. Alm. Does a seller's e-commerce reputation matter? J. Indust. Econom., 50(3):337--349, 2002.
• 11: U.S. Department of Justice. Internet fraud. http://www.internetfraud.usdoj.gov. 2002.
• 12: P. Resnick and R. Zeckhauser. Trust among strangers in internet transactions: empirical analysis of ebay's reputation system. The economics of the Internet and e-commerce, 11:127--157, 2002.
• 13: Paul Resnick , Ko Kuwabara , Richard Zeckhauser , Eric Friedman, Reputation systems, Communications of the ACM, v.43 n.12, p.45-48, Dec. 2000 [doi>10.1145/355112.355122]
• 14: P. Resnick, R. Zeckhauser, J. Swanson, and K. Lockwood. The value of reputation on ebay: A controlled experiment. Working paper originally presented at the ESA conference, June 2002.

INDEX TERMS

Primary Classification:
  H. Information Systems
  H.1 MODELS AND PRINCIPLES
      H.1.m Miscellaneous

General Terms:
Reliability

Keywords:
reputation systems