We show that endogenous firm selection provides a new welfare margin for heterogeneous firm models of trade (relative to homogeneous firm models). Under some parameter restrictions, the trade elasticity is constant and is a sufficient statistic for welfare, along with the domestic trade share....

This chapter reviews the new approach to international trade based on firm heterogeneity in differentiated product markets. This approach explains a variety of features exhibited in disaggregated trade data, including the higher productivity of exporters relative to non-exporters,...

We show that endogenous firm selection provides a new welfare margin for heterogeneous firm models of trade (relative to homogeneous firm models). Under some parameter restrictions, the trade elasticity is constant and is a sufficient statistic for welfare, along with the domestic trade share....

This paper reviews the recent theoretical literature on heterogeneous firms and trade, which emphasizes firm selection into international markets and reallocations of resources across firms. We discuss the empirical challenges that motivated this research and its relationship to traditional...