We use highly disaggregated firm-level export data from Costa Rica, Ecuador, and Uruguay over the period 2005-2008 to provide a precise characterization of firms' export margins, across products, destination countries, and crucially customers. We show that a firm's number of buyers and the...

This paper studies how firm heterogeneity in terms of productivity affects the balance between agglomeration and dispersion forces in the presence of pecuniary externalities through a selection model of monopolistic competition with variable mark-ups. It shows that firm heterogeneity matters....

The global welfare implications of home market effects in trade models with imperfect competition are little understood. This paper proposes a simple model in which such implications can be easily analyzed. It shows an overall tendency of imperfectly competitive sectors to inefficiently cluster...