A number of stylized facts have been documented about the extensive margin of trade - which firms export, and how many products they send to how many destinations. We argue that the sparse nature of trade data is crucial to understanding these stylized facts. Typically the number of observations...

We consider a very general class of public finance problems that encompasses the Ramsey model of optimal taxation as well as economies with limited commitment, private information, and political economy frictions, and allows for incomplete markets. We identify a sufficient condition to rule out...