An intermediary serves as a platform through which a producer with a private cost sells a product to a unit mass of consumers. The intermediary has information about the match values between consumers and the product, which can be used to inform both the consumers and the producer. This paper studies the revenue-maximizing mechanisms for the intermediary under two critical business models: the retail model and the marketplace model. We show that the market outcomes are equivalent across the two business models. Furthermore, it is optimal for the intermediary to either (i) provide upper-censored partial information to consumers and no information to the producer, or (ii) fully inform consumers about their values and partially disclose that information to the producer and induce quasi-perfect price discrimination. This result suggests that product recommendation and price discrimination are outcome-equivalent mechanisms for an intermediary. 

This paper studies sequential social learning, in which agents learn about an underlying state from others' actions. In contrast to the classic models with a network observational structure, agents arrive in cohorts and observe action-signals regarding previous cohorts' actions. We identify a simple, necessary, and sufficient condition for asymptotic learning, called separability, a joint property of action-signals and agents' private information about the state. A necessary condition for separability is "unbounded beliefs" which requires agents' private information to generate strong evidence of the true state, even if the probability of such evidence is small. With unbounded beliefs, separability is satisfied if action-signals have double thresholds so that, at a minimum, they reveal whether agents above a threshold number in each cohort choose actions below a choice-threshold. Without double thresholds, learning can be confounded so that agents always choose different actions with positive probabilities and never reach a consensus. 

This paper examines the welfare implications of third-party informational intermediation. A seller sets the price of a product that is sold through an informational intermediary. The intermediary can disclose information about the product to consumers and earn a fixed percentage of sales revenue in each period. The intermediary's market base grows at a rate that increases with past consumer surplus. We characterize the stationary equilibria and the set of subgame perfect equilibrium payoffs. When market feedback (i.e., the extent to which past consumer surplus affects future market bases) increases, welfare may decrease in the Pareto sense.

A long-lived seller sells a new product of unknown value by offering prices and recommendations to short-lived consumers in continuous time. The seller receives feedback about the product at a rate that increases with the instantaneous sales volume. The optimal selling mechanism features episodes of price discounts, during which the seller discontinuously lowers the price and selectively sends out unwarranted recommendations to consumers. The optimal price path differs for niche and mass products and may involve delayed discounts, below-cost pricing, and dynamic price back-tracking.

Delivery costs are a major component of trade costs. This paper studies the pricing of delivery services and the associated welfare implications. We develop a theoretical model to analyze the optimal two-part pricing of delivery services when delivery firms must commit to the maximum capacity for a round trip due to the backhaul problem and face heterogeneous demands across different geographical regions. The model predicts that a reduction in a delivery firm’s shipping costs partially lowers the marginal delivery price, raises the fixed fees, and has asymmetric impacts on prices across the fronthaul and backhaul routes. Using newly collected data from the largest informatics platform for Chinese e-commerce delivery firms, we quantify the model and find that a universal 10% reduction in shipping costs leads the marginal price to drop by 2.35%, the fixed fee to increase by 0.82%, delivery firms’ profit to increase by 1.17%, and e-commerce sellers’ welfare to rise by 0.36%, on average, with sellers in eastern and coastal cities gaining more than those in western and hinterland cities.