This paper argues that the theoretical foundations for the gravity equation are general, while the empirical performance of the gravity equation is specific to the type of goods examined. Most existing theory for the gravity equation depends on the assumption of differentiated goods. We show...

This paper develops a procedure to rank-order countries and commodities using disaggregated US imports data. It finds strong evidence that both countries and commodities can be ranked, consistent with the ‘product cycle’ hypothesis. Countries habitually begin to export goods to the United...