We consider the optimal taxation of a good which exhibits a negative externality, in a setting where agents differ in their value for the good, their disutility for the externality and their value for money, and the planner observes neither. Pigouvian taxation is the unique Pareto efficient...

We study the effects of allocative and informational externalities in (multi-object) auctions and related mechanisms. Such externalities naturally arise in models that embed auctions in larger economic contexts. In particular, they appear when there is downstream interaction among bidders after...