Northern exposure: a field experiment measuring externalities between search advertisements

"North" ads, or sponsored listings appearing just above the organic search results, generate the majority of clicks and revenues for search engines. In this paper, we ask whether the competing north ads exert externalities on each other. In particular, does increasing the number of rival north ads decrease the number of clicks I receive on my own north ad? We conduct a controlled experiment to investigate this question and find, to our surprise, that additional rival ads in the north tend to increase rather than decrease the click-through rate (CTR) of the top sponsored listing. We propose several possible explanations for this phenomenon, and point out directions for new theoretical models of sponsored search.

[1]  David H. Reiley,et al.  Demand Reduction in Multi-Unit Auctions: Evidence from a Sportscard Field Experiment: Reply , 2005 .

[2]  Dean S. Karlan,et al.  Does Price Matter in Charitable Giving? Evidence from a Large-Scale Natural Field Experiment , 2006 .

[3]  David Lucking-Reiley,et al.  Using field experiments to test equivalence between auction formats: Magic on the internet , 1999 .

[4]  Nicole Immorlica,et al.  Externalities in Keyword Auctions: An Empirical and Theoretical Assessment , 2009, WINE.

[5]  G. Harrison,et al.  Field experiments , 1924, The Journal of Agricultural Science.

[6]  B. Schwartz.  The Paradox of Choice: Why More Is Less , 2004 .

[7]  Mohammad Mahdian,et al.  A Cascade Model for Externalities in Sponsored Search , 2008, WINE.

[8]  Mohammad Mahdian,et al.  Externalities in online advertising , 2008, WWW.

[9]  David Lucking-Reiley,et al.  Demand reduction in multiunit auctions: Evidence from a sportscard field experiment , 2004 .

[10]  Jonathan Robinson,et al.  Nudging Farmers to Use Fertilizer: Theory and Experimental Evidence from Kenya , 2009 .

[11]  O. Bandiera,et al.  Social preferences and the response to incentives: Evidence from personnel data , 2005 .

[12]  J. Angrist,et al.  Journal of Economic Perspectives—Volume 15, Number 4—Fall 2001—Pages 69–85 Instrumental Variables and the Search for Identification: From Supply and Demand to Natural Experiments , 2022 .

[13]  Glenn Ellison,et al.  Position Auctions with Consumer Search , 2007 .

[14]  K. Arrow,et al.  The New Palgrave Dictionary of Economics , 2020 .

[15]  A. Tversky,et al.  The framing of decisions and the psychology of choice. , 1981, Science.

[16]  David Lucking-Reiley,et al.  The Effects of Seed Money and Refunds on Charitable Giving: Experimental Evidence from a University Capital Campaign , 2002, Journal of Political Economy.

[17]  Nolan Miller,et al.  Giffen Behavior and Subsistence Consumption. , 2008, The American economic review.