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International Trade With Heterogeneous Firms: Theory and Evidence  

Alessandra Bonfiglioli, Rosario Crinò, and Gino Gancia

International trade is dominated by a small number of very large firms. Models of trade with heterogeneous firms have been developed to study the causes and consequences of this observation. The canonical model of trade with heterogeneous firms shows that trade leads to between-firm reallocations and selection: It shifts employment toward firms with the best attributes and forces marginal firms to exit. The model also illustrates the role of heterogeneity, and its various sources, in explaining the volume of trade and the firm-level margins of adjustment. Consistent with the model, the empirical literature has documented that exporting is a rare activity, that exporting firms are larger and more productive than other firms, and that trade liberalization reallocates market shares toward the best-performing firms in various countries. Studies using transaction-level data have unveiled additional salient features of trade flows. First, sales by foreign firms are very heterogeneous and highly concentrated. Second, both the extensive margin (number of exporting firms) and the intensive margin (average export per firm) are important in explaining the level of exports and its changes over time. More heterogeneity in sales across firms is associated with a higher volume of trade along both margins. Third, increased foreign competition reallocates market shares toward top firms and hence can increase concentration from any country of origin. Numerous extensions of the benchmark model have been proposed to study other important aspects, such as the relevance of multi-product and multinational firms, the import behavior of firms, and the extent to which heterogeneity is endogenous to firms’ choices, but some open challenges still remain.


Heterogeneous Firms, Trade Liberalization, and Welfare  

Alan Spearot

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.


International Trade, Wages, and Unemployment  

Priyaranjan Jha

Traditional trade theory has focused on the allocation of resources between various sectors of the economy and how it changes in response to trade liberalization while maintaining the assumption of free mobility of resources across sectors within an economy. This simplifying assumption is at odds with empirical evidence which shows considerable frictions in the movement of resources between sectors, at least in the short to medium run. Workers who lose their jobs in the import competing sector may find it hard to find a job immediately in the export sector. This has given rise to a growing literature that incorporates frictions in the mobility of factors of production in general, and labor in particular, in trade models. This article surveys the literature on trade and unemployment where unemployment is caused by search frictions or wage rigidity of some kind such as minimum wage, efficiency wage, or implicit contracts. While the focus is on unemployment, any model studying the impact of trade on labor markets features wage effects, too, and a brief discussion of wage effects is also provided. Trade affects unemployment in these multi-sector models through two main channels: sectoral unemployment rates and intersectoral reallocation of resources. In newer trade models with heterogeneous firms, trade can change unemployment by affecting the allocation of resources within a sector. While the theoretical models in this literature identify various channels through which trade liberalization affects unemployment, many of these channels have opposing implications for unemployment, rendering the net effect of trade liberalization on unemployment ambiguous in many settings. This has also given rise to an empirical literature studying the implications of trade liberalization on unemployment.