Ineffective institutions increase transaction costs and reduce trade. This paper shows that differences in the effectiveness of institutions offer an explanation for the tendency of OECD countries to trade disproportionately with each other, and with non-OECD countries.

To estimate correctly the effect of variable trade costs on firms’ exports, the gravity equation should control for the number of firms that participate in foreign markets. Due to the absence of these data, previous studies control for this omitted variable using econometric strategies that...