Essays on the Design of Online Marketplaces and Platforms

This dissertation consists of three chapters that concern the design of online marketplaces and platforms. In Chapter 1, I estimate the impact of increasing the extent to which content recommendations are personalized by analyzing the results of a randomized experiment on approximately 900,000 Spotify users across seventeen countries. I find that increasing recommendation personalization increased the number of podcasts that Spotify users streamed, but also decreased the individual-level diversity of Spotify users’ podcast consumption and increased the dissimilarity between the podcast consumption patterns of different users across the population. In Chapter 2, I propose methods for obtaining unbiased estimates of the total average treatment effect (TATE) when conducting experiments in online marketplaces, and test the viability of said methods using a simulation built on top of scraped data from Airbnb. I find that blocked graph cluster randomization can reduce the bias of TATE estimates in online marketplaces by as much as 64.5%, however, this reduction in bias comes with a substantial increase in root-mean-square error (RMSE). I also find that fractional neighborhood treatment response (FNTR) exposure models and inverse probability-weighted estimators have the potential to further reduce bias, depending on the choice of FNTR threshold. In Chapter 3, I conduct two large-scale meta-experiments on Airbnb in an attempt to estimate the actual magnitude of bias in TATE estimates from marketplace interference. In both meta-experiments, some Airbnb listings are assigned to experiment conditions at the individual-level, whereas others are assigned to experiment conditions at the level of clusters of listings that are likely to substitute for one another. The two meta-experiments measure the impact of two different pricing-related interventions on Airbnb: a change to Airbnb’s fee policy, and a change to the pricing algorithm that Airbnb uses to recommend prices to sellers. Results from the fee policy meta-experiment reveal that at least 32.60% of the treatment effect estimate in the Bernoulli-randomized meta-experiment arm is due to interference bias. Results from the pricing algorithm meta-experiment highlight the difficulty of detecting interference bias when treatment interventions require intention-to-treat analysis.Ph.D