This dissertation is a collection of three essays in the fields of international trade and industrial organization. The first two chapters study the macroeconomic implications of firm heterogeneity. In the first chapter, I use data on the universe of French manufacturing exporters from 1994-2001 to study the relationship between international trade and the manufacturing labor share. In particular, I investigate how and to what extent changes in demand conditions on foreign markets impact the labor share. This chapter aims to shed light on whether international trade may affect the labor share through channels other than changes in import exposure. In the second chapter, which is joint work with Flavien Moreau, we study the cost of distortio...