A Cascade Model for Externalities in Sponsored Search

  • David Kempe
  • Mohammad Mahdian
Part of the Lecture Notes in Computer Science book series (LNCS, volume 5385)


One of the most important yet insufficiently studied issues in online advertising is the externality effect among ads: the value of an ad impression on a page is affected not just by the location that the ad is placed in, but also by the set of other ads displayed on the page. For instance, a high quality competing ad can detract users from another ad, while a low quality ad could cause the viewer to abandon the page altogether.

In this paper, we propose and analyze a model for externalities in sponsored search ads. Our model is based on the assumption that users will visually scan the list of ads from the top to the bottom. After each ad, they make independent random decisions with ad-specific probabilities on whether to continue scanning. We then generalize the model in two ways: allowing for multiple separate blocks of ads, and allowing click probabilities to explicitly depend on ad positions as well. For the most basic model, we present a polynomial-time incentive-compatible auction mechanism for allocating and pricing ad slots. For the generalizations, we give approximation algorithms for the allocation of ads.


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  1. 1.
    Aggarwal, G., Feldman, J., Muthukrishnan, S., Pál, M.: Sponsored search auctions with markovian users. In: Proc. 4th Workshop on Ad Auctions (2008)Google Scholar
  2. 2.
    Aggarwal, G., Goel, A., Motwani, R.: Truthful auctions for pricing search keywords. In: Proc. 8th ACM Conf. on Electronic Commerce, pp. 1–7 (2006)Google Scholar
  3. 3.
    Athey, S., Ellison, G.: Position auctions with consumer search. Working Paper (September 2007)Google Scholar
  4. 4.
    Cary, M., Das, A., Edelman, B., Giotis, I., Heimerl, K., Karlin, A., Mathieu, C., Schwarz, M.: Greedy bidding strategies for keyword auctions. In: Proc. 9th ACM Conf. on Electronic Commerce, pp. 262–271 (2007)Google Scholar
  5. 5.
    Clarke, E.: Multipart pricing of public goods. Public Choice 11, 17–33 (1971)CrossRefGoogle Scholar
  6. 6.
    Craswell, N., Zoeter, O., Taylor, M., Ramsey, B.: An experimental comparison of click position-bias models. In: Proc. 1st Intl. Conf. on Web Search and Data Mining (2008)Google Scholar
  7. 7.
    Das, A., Giotis, I., Karlin, A., Mathieu, C.: On the effects of competing advertisements in keyword auctions (May 2008) (unpublished manuscript)Google Scholar
  8. 8.
    Edelman, B., Ostrovsky, M., Schwarz, M.: Internet advertising and the generalized second price auction: Selling billions of dollars worth of keywords. American Economic Review 97(1), 242–259 (2007)CrossRefGoogle Scholar
  9. 9.
    Ghosh, A., Mahdian, M.: Externalities in online advertising. In: 17th Intl. World Wide Web Conference (2008)Google Scholar
  10. 10.
    Groves, T.: Incentives in teams. Econometrica 41, 617–631 (1973)MathSciNetCrossRefMATHGoogle Scholar
  11. 11.
    Joachims, T., Granka, L., Pan, B., Hembrooke, H., Radlinski, F., Gay, G.: Evaluating the accuracy of implicit feedback from clicks and query reformulations in web search. ACM Transactions on Information Systems (TOIS) 25(2) (2007)Google Scholar
  12. 12.
    Lahaie, S.: An analysis of alternative slot auction designs for sponsored search. In: Proc. 8th ACM Conf. on Electronic Commerce, pp. 218–227 (2006)Google Scholar
  13. 13.
    Lahaie, S., Pennock, D., Saberi, A., Vohra, R.: Sponsored search auctions. In: Nisan, N., Roughgarden, T., Tardos, É., Vazirani, V. (eds.) Algorithmic Game Theory, ch. 28. Cambridge University Press, Cambridge (2007)Google Scholar
  14. 14.
    Mahdian, M., Nazerzadeh, H., Saberi, A.: Allocating online advertisement space with unreliable estimates. In: Proc. 9th ACM Conf. on Electronic Commerce, pp. 288–294 (2007)Google Scholar
  15. 15.
    Muthukrishnan, S., Pál, M., Svitkina, Z.: Stochastic models for budget optimization in search-based advertising. In: Deng, X., Graham, F.C. (eds.) WINE 2007. LNCS, vol. 4858, pp. 131–142. Springer, Heidelberg (2007)CrossRefGoogle Scholar
  16. 16.
    Varian, H.: Position auctions. Intl. J. of Industrial Organization 25(6), 1163–1178 (2007)CrossRefGoogle Scholar
  17. 17.
    Vickrey, W.: Counterspeculation, auctions, and competitive sealed tenders. J. of Finance 16, 8–37 (1961)MathSciNetCrossRefGoogle Scholar
  18. 18.
    Wortman, J., Vorobeychik, Y., Li, L., Langford, J.: Maintaining equilibria during exploration in sponsored search auctions. In: Deng, X., Graham, F.C. (eds.) WINE 2007. LNCS, vol. 4858, pp. 119–130. Springer, Heidelberg (2007)CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2008

Authors and Affiliations

  • David Kempe
    • 1
  • Mohammad Mahdian
    • 2
  1. 1.University of Southern CaliforniaLos AngelesUSA
  2. 2.Yahoo! ResearchSanta ClaraUSA

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