Three sources of gains from trade under monopolistic competition are (i) new import varieties available to consumers; (ii) enhanced efficiency as more productive firms begin exporting and less productive firms exit; (iii) reduced markups charged by firms due to import competition. The first...

The simple gravity equation explains a great deal about the data on bilateral trade flows and is consistent with several theoretical models of trade. We argue that alternative theories nevertheless predict subtle differences in key parameter values, depending on whether goods are homogeneous or...