市场营销学系学术讲座（11月19日）

Misinformation and Mistrust:The Equilibrium Effects of Fake Reviews on Amazon.com

Speaker: Brett Hollenbeck

Associate Professor

UCLA Anderson School of Management

Time: 13:00-14:30, Nov.19^th (Wednesday), 2025

Venue：Siyuan Building, Room 624

MC: Prof. Yunlu Yin

Abstract:

Fake product reviews—and the manipulation of reputation systems by sellers more broadly—are a widespread issue for two-sided platforms. We study two primary channels through which such manipulation can affect market outcomes: (i) creating misinformation about the reviewed product, and (ii) breeding mistrust in ratings system overall. To examine these in the Amazon.com marketplace, we measure misinformation by observing products purchasing fake reviews and measure mistrust by eliciting shoppers’ beliefs about the prevalence of fake reviews on Amazon through an incentivized survey experiment. We incorporate these into a structural model of demand in which consumers form beliefs about product quality based on observed reviews and perceptions about their trustworthiness. Counterfactual policy simulations indicate that fake reviews reduce consumer welfare, shift sales from honest to dishonest sellers, and ultimately harm the platform. Welfare losses arise primarily from misinformation that leads to worse purchases. While mistrust also leads to purchasing mistakes, the consumer harms of mistrust are largely offset by increased price competition under a weakened ratings system. Finally, we identify key limitations in platforms’ incentives to police manipulation and evaluate enforcement alternatives.

Bio:

Brett Hollenbeck earned a PhD in Economics from the University of Texas at Austin. His research focuses on topics at the intersection of economics and marketing, with an emphasis on how online reviews and ratings affect consumer decision-making and market competition. He has also conducted research on customer loyalty programs, e-commerce advertising strategies, retail promotions on social media, and privacy regulation. In addition, Professor Hollenbeck has studied horizontal mergers and innovation in concentrated markets.

Professor Hollenbeck publishes articles in peer-reviewed marketing and economics journals, including Marketing Science, the Journal of Marketing Research, and the RAND Journal of Economics. He serves on multiple editorial boards of academic journals and is an associate editor at Management Science and Marketing Science.