Structural Gravity Equations with Intensive and Extensive Margins
New trade models with heterogeneous firms have had a consequent influence on gravity equations. According to Chaney (2007) and Melitz and Ottaviano (2005), the theoretical relationship between trade costs and trade flows is the sum of the effect of trade costs on the number of exporting firms (the extensive margin) and the value of individual exports (the intensive margin). The distinctive effect of distance on the two margins deeply modifies predictions of the trade literature, among which the sectoral effect of trade policies. Using French firms-level export data to 61 countries, on the period 1989-1992, we provide unbiased structural estimates of the three parameters governing trade elasticities with respect to distance. This dissection of the gravity equation provides consistent evidence in favor of heterogeneous firms models of trade.
Recent trade models with heterogenous firms have considerable consequences on the interpretation of gravity equations. Chaney (2008) shows that the effect of distance on trade margins incorporates three parameters: the elasticity of substitution between goods, the elasticity of trade costs with respect to distance, and the degree of firm heterogeneity. We structurally estimate the parameters of trade flows in Chaney’s model using French firm-level export data for 1986-1992, and controlling for the fixed costs of exporting. Our estimated parameters are consistent, for 27 out of 34 industries, with the theoretical model. They also allow us to evaluate the effects of transport cost separately from the effects of tarifs, without having to resort to detailed data on trade frictions.
Gravity equations; international trade; firm heterogeneity
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