Many retail platforms have recently expanded their advertising businesses, featuring sponsored products in search results. While sponsored product advertising can enable sellers to reveal information, it can also worsen search results and raise prices. Using data on Amazon searches, purchases, and advertising auction bids, I estimate a model incorporating consumers, sellers, and the platform to evaluate the welfare effects. Counterfactual analysis suggests that eliminating advertising could benefit consumers and sellers under a fixed commission rate, but would harm them if Amazon adjusts the rate optimally. Advertising tends to be more beneficial in markets with newer products and greater product differentiation.

Concerned about the low academic ability of public school teachers, in the 1990s and 2000s, some states increased licensing stringency to weed out candidates with low academic ability, while others decreased restrictions in hopes of attracting more competitive candidates. We offer a theoretical model justifying both reactions. Using data from 1991–2007 on licensing requirements and teacher characteristics, we find that stricter licensing requirements, specially those emphasizing academic coursework, increased the left tail of the distribution of college selectivity among secondary school teachers. We find no evidence of disparate effects for high-minority or high-poverty school districts.

This paper documents a robust pattern from diverse sequential bargaining settings: agents favor offers that split the difference between the previous two offers. Our empirical settings include used cars, insurance claims, home sales, trade tariffs, a TV game show, eBay, and auto-rickshaws. These even-split offers are more likely to be accepted, less likely to spur exit by the opponent, and more likely to be followed by subsequent split-the-difference offers if bargaining continues. We propose several theoretical frameworks to explain this behavior, including an inference argument under which split-the-difference offers can be viewed as an equal split of the potential surplus. 

We study the equilibrium effects of introducing competitive bidding in drug procurement. In 2019, China introduced a competitive bidding program where drug companies bid for a prespecified procurement quantity in nine provinces. Using a difference-in-differences design, we show that the program reduced average drug prices by 47.4%. Generic drugs won most bids and cut prices by 75.0%. We develop an equilibrium model to quantify the trade-off between lower prices and potential choice distortions. Competitive bidding increases consumer welfare if policymakers believe consumers should value branded and bioequivalent generic drugs equally. The program also reduced government expenditure on insurance by 19.8%.

This paper investigates the welfare effects of vertical integration in China's movie industry. We leverage data covering all theaters and 423 popular movies in China during 2014-2018. We find no evidence of integrated movies being foreclosed to rival theaters. Integrated theaters show their movies for longer, allocate more screenings, and charge lower prices. We estimate a model of consumers' demand and theaters' screening decisions. Integrated theaters internalize a substantial fraction of their upstream companies' profits. Vertical integration both mitigates distortions from revenue-sharing contracts and steers demand favoring integrated movies. Overall, vertical integration increases consumer surplus with considerable heterogeneity across markets.

Physicians, judges, teachers, and agents in many other settings differ systematically in the decisions they make when faced with similar cases. Standard approaches to interpreting and exploiting such differences assume they arise solely from variation in preferences. We develop an alternative framework that allows variation in preferences and diagnostic skill and show that both dimensions may be partially identified in standard settings under quasi-random assignment. We apply this framework to study pneumonia diagnoses by radiologists. Diagnosis rates vary widely among radiologists, and descriptive evidence suggests that a large component of this variation is due to differences in diagnostic skill. Our estimated model suggests that radiologists view failing to diagnose a patient with pneumonia as more costly than incorrectly diagnosing one without, and that this leads less skilled radiologists to optimally choose lower diagnostic thresholds. Variation in skill can explain 39% of the variation in diagnostic decisions, and policies that improve skill perform better than uniform decision guidelines. Failing to account for skill variation can lead to highly misleading results in research designs that use agent assignments as instruments.

In recent years, there has been widespread concern that misinformation on social media is damaging societies and democratic institutions. In response, social media platforms have announced actions to limit the spread of false content. We measure trends in the diffusion of content from 569 fake news websites and 9540 fake news stories on Facebook and Twitter between January 2015 and July 2018. User interactions with false content rose steadily on both Facebook and Twitter through the end of 2016. Since then, however, interactions with false content have fallen sharply on Facebook while continuing to rise on Twitter, with the ratio of Facebook engagements to Twitter shares decreasing by 60%. In comparison, interactions with other news, business, or culture sites have followed similar trends on both platforms. Our results suggest that the relative magnitude of the misinformation problem on Facebook has declined since its peak.

Over the last decade, market share in video entertainment services has shifted from traditional cable bundles towards direct-to-consumer (DTC) streaming services such as Netflix and Disney+. This paper examines the effect of such a shift on consumers and firm profits using a model of viewership and subscription choice by consumers together with content pricing and content investment by firms. We estimate the model using data on viewership, subscription market shares, pricing, content availability, and content expenditures. Using data up to 2017, prior to the launch of multiple major streaming services, the model predicts well the market share of new streaming services that entered by 2023. We use the estimated model to explain why some niche streaming services have not been successful, to predict the effect of moving NFL telecasts to Netflix, and to predict that an equilibrium featuring bundles of streaming services results in a superior welfare outcome than a balkanized equilibrium of only individual streaming services.