We study competition in two sided markets with common network externality rather than with the standard inter-group e¤ects. This type of externality occurs when both groups benefit, possibly with different intensities, from an increase in the size of one group and from a decrease in the size of...

This paper studies a market for a medical product in which there is perfect competition among health insurers, while the good is sold by a monopolist. Individuals differ in their severity of illness and there is ex post moral hazard. We consider two regimes: one in which insurers use coinsurance...

We study optimal income taxation in a framework where one's willingness to report his income truthfully is positively correlated with his type. We show that allowing low-productivity types to cheat leads to Pareto-superior outcomes as compared to deterring them, even if audits can be performed...

We consider an unhealthy good, such as a sugar-sweetened beverage, the health damages of which are misperceived by consumers. The sugar content is endogenous. We first study the solution under “pseudo” perfect competition. In that case a simple Pigouvian tax levied per unit of output but...