What Drives Extremity Bias in Online Reviews? Theory and Experimental Evidence

50 Pages Posted: 6 Sep 2019 Last revised: 11 Sep 2019

See all articles by Leif Brandes

Leif Brandes

University of Lucerne

David Godes

University of Maryland

Dina Mayzlin

University of Southern California - Marshall School of Business

Date Written: September 10, 2019

Abstract

In a range of studies across platforms, online ratings have been shown to be characterized by distributions with disproportionately-heavy tails. We focus on understanding the underlying process that yields such “j-shaped” or “extreme” distributions. We develop a simple analytical model to capture the most-common explanations: differences in utility or differences in base rates associated with posting extreme versus moderate reviews. We compare the predictions of these explanations with those of an alternative theory based on differential rates of attrition from the potential reviewer pool across people with moderate versus extreme experiences. The attrition rate, by assumption, is higher for moderate reviews. The three models yield starkly different predictions with respect to the impact on the relative prevalence of extreme versus moderate reviews of a review solicitation email: while existing theories predict a relative increase in extreme reviews, our attrition-based model predicts a decrease. Our results from a large-scale field experiment with an online travel platform clearly support the predictions from the attrition-based explanation, but are inconsistent with those from the utility-based and base-rate explanations alone.

Keywords: online reviews, online word of mouth, field experiment

Suggested Citation

Brandes, Leif and Godes, David and Mayzlin, Dina, What Drives Extremity Bias in Online Reviews? Theory and Experimental Evidence (September 10, 2019). Available at SSRN: https://ssrn.com/abstract=3449159 or http://dx.doi.org/10.2139/ssrn.3449159

Leif Brandes

University of Lucerne ( email )

Lucerne
Switzerland

David Godes

University of Maryland ( email )

College Park
College Park, MD 20742
United States

Dina Mayzlin (Contact Author)

University of Southern California - Marshall School of Business ( email )

701 Exposition Blvd
Los Angeles, CA 90089
United States
213-740-3360 (Phone)

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