We examine the effect of consumer reviews on relative sales of books on Amazon.com and BarnesandNoble.com. We find that 1) reviews are overwhelmingly positive at both sites, but there are more reviews and longer reviews at Amazon.com, 2) an improvement in a book's reviews leads to an increase in...

Search frictions can explain why the "law of one price" fails in retail markets and why even firms selling commodity products have pricing power. In online commerce, physical search costs are low, yet price dispersion is common. We use browsing data from eBay to estimate a model of consumer...

Platform marketplaces can potentially steer buyers to certain sellers by recommending or guaranteeing those sellers. Money-back guarantees—which create a direct financial stake for the platform in seller performance—might be particularly effective at steering, as they align buyer and...

Digitization has led to product proliferation, straining traditional institutions for product discovery; but digitization has also spawned crowd-based rating systems. We compare the relative impacts of professional critics and crowd-based Amazon star ratings on consumer welfare in book...

This paper examines a model in which advertisers bid for "sponsored-link" positions on a search engine. The value advertisers derive from each position is endogenized as coming from sales to a population of consumers who make rational inferences about firm qualities and search optimally....

The internet has dramatically reduced the cost of varying prices, displays and information provided to consumers, facilitating both active and passive experimentation. We document the prevalence of targeted pricing and auction design variation on eBay, and identify hundreds of thousands of...

Increased competition from the internet has raised concerns about the quality of prescription drugs sold online. Given the pressure from the Department of Justice, Google agreed to ban pharmacies not certified by the National Association of Boards of Pharmacy (NABP) from sponsored search...

Quality certification programs help consumers to identify high-quality products or sellers in markets with information asymmetries. Using data from eBay UK's online marketplace, we study how certification's impact on consumer demand varies with market- and seller-level attributes, exploiting...

This paper shows that accounting for variation in mistakes can be crucial for welfare analysis. Focusing on consumer underreaction to not-fully-salient sales taxes, we show theoretically that the efficiency costs of taxation are amplified by differences in underreaction across individuals and...

A growing body of empirical literature finds that consumers are relatively limited in how much they search over product characteristics. We assemble a dataset of search and purchase behavior from eBay to quantify the returns, and thus implied costs, to consumer search on the internet. The...