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Why Voluntary Contributions? Google Answers


  • Tobias Regner


We study the pricing and tipping behaviour of users of the online service `Google Answers'. While they set a price for the answer to their question ex ante, they can additionally give a tip to the researcher ex post. We develop a model that is based on reciprocal theories of social preferences pioneered by Rabin (1993) and extended by Dufwenberg and Kirchsteiger (2004). The predictions of our model are empirically tested with the field data we obtained. The reasons for leaving a tip are analysed. A significant amount of users are motivated by social preferences. We also find strong support for reputation concerns. Moreover, researchers appear to adjust their effort based on the user's previous tipping behaviour. We conclude that an endogenous incomplete contracts design encourages people to contribute voluntarily. This is motivated by reciprocity when people are socially minded, but also generally by strategic behaviour to build up a good reputation. Efficiency is increased when contracts are left open deliberately as high effort is sustained.

Suggested Citation

  • Tobias Regner, 2005. "Why Voluntary Contributions? Google Answers," The Centre for Market and Public Organisation 05/115, Department of Economics, University of Bristol, UK.
  • Handle: RePEc:bri:cmpowp:05/115

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    References listed on IDEAS

    1. Gary Charness & Matthew Rabin, 2002. "Understanding Social Preferences with Simple Tests," The Quarterly Journal of Economics, Oxford University Press, vol. 117(3), pages 817-869.
    2. Ernst Fehr & Simon Gachter & Georg Kirchsteiger, 1997. "Reciprocity as a Contract Enforcement Device: Experimental Evidence," Econometrica, Econometric Society, vol. 65(4), pages 833-860, July.
    3. Luis Cabral & Ali Hortacsu, 2004. "The Dynamics of Seller Reputation: Theory and Evidence from eBay," NBER Working Papers 10363, National Bureau of Economic Research, Inc.
    4. Ernst Fehr & Alexander Klein & Klaus M. Schmidt, "undated". "Fairness, Incentives and Contractual Incompleteness," IEW - Working Papers 072, Institute for Empirical Research in Economics - University of Zurich.
    5. John A. List, 2004. "Young, Selfish and Male: Field evidence of social preferences," Economic Journal, Royal Economic Society, vol. 114(492), pages 121-149, January.
    6. Dufwenberg, Martin & Kirchsteiger, Georg, 2004. "A theory of sequential reciprocity," Games and Economic Behavior, Elsevier, vol. 47(2), pages 268-298, May.
    7. Ernst Fehr & Klaus M. Schmidt, "undated". "Theories of Fairness and Reciprocity - Evidence and Economic Applications," IEW - Working Papers 075, Institute for Empirical Research in Economics - University of Zurich.
    8. Cragg, John G, 1971. "Some Statistical Models for Limited Dependent Variables with Application to the Demand for Durable Goods," Econometrica, Econometric Society, vol. 39(5), pages 829-844, September.
    9. Geanakoplos, John & Pearce, David & Stacchetti, Ennio, 1989. "Psychological games and sequential rationality," Games and Economic Behavior, Elsevier, vol. 1(1), pages 60-79, March.
    10. Azar, Ofer H., 2004. "The history of tipping--from sixteenth-century England to United States in the 1910s," Journal of Behavioral and Experimental Economics (formerly The Journal of Socio-Economics), Elsevier, vol. 33(6), pages 745-764, December.
    11. Rabin, Matthew, 1993. "Incorporating Fairness into Game Theory and Economics," American Economic Review, American Economic Association, vol. 83(5), pages 1281-1302, December.
    12. Amemiya, Takeshi, 1984. "Tobit models: A survey," Journal of Econometrics, Elsevier, vol. 24(1-2), pages 3-61.
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    Cited by:

    1. Regner, Tobias, 2014. "Social preferences? Google Answers!," Games and Economic Behavior, Elsevier, vol. 85(C), pages 188-209.

    More about this item


    social preferences; reciprocity; moral hazard; reputation; internet;

    JEL classification:

    • C24 - Mathematical and Quantitative Methods - - Single Equation Models; Single Variables - - - Truncated and Censored Models; Switching Regression Models; Threshold Regression Models
    • C70 - Mathematical and Quantitative Methods - - Game Theory and Bargaining Theory - - - General
    • C93 - Mathematical and Quantitative Methods - - Design of Experiments - - - Field Experiments
    • D82 - Microeconomics - - Information, Knowledge, and Uncertainty - - - Asymmetric and Private Information; Mechanism Design
    • L86 - Industrial Organization - - Industry Studies: Services - - - Information and Internet Services; Computer Software

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