Summary

While the modern theory of international trade allows for many different modeling assumptions, the gains from trade can often be calculated using a common set of statistics. In particular, the share of a country’s output that is consumed domestically, the elasticity of bilateral trade with respect to trade costs, and the relationship between markups and firm size, each have a clear role in the gains from integration. All of these statistics may also be structurally linked to the degree of firm heterogeneity, usually the dispersion in firm-level productivity. Accordingly, the presence of firm heterogeneity may have a meaningful impact on the welfare response to trade liberalization. A quantitative application of a common firm heterogeneity model indicates that increased dispersion of firm-level productivity has a disproportionately large and positive impact on the gains from trade for smaller, less-developed countries.