This paper examines how factor proportions determine product varieties, or the extensive margin, in exports of countries. A model of the economy with two countries, two factors, and a multitude of industries with productivity-heterogeneous firms explains the relative number of export varieties...

This paper investigates how the fraction of exporting firms among domestic firms in a country differs across industries, depending on a country’s comparative advantage. A model, which extends work by Melitz (2003) and Bernard, Redding and Schott (2007), describes an economy that comprises two...