The authors develop a framework for studying trade in horizontally and vertically differentiated products. In their model, consumers with heterogeneous incomes and tastes purchase a homogeneous good and make a discrete choice of quality and variety of a differentiated product. The distribution...

This Economica Coase Lecture reviews research that has revolutionized the field of international trade and foreign direct investment. It explains the motivation behind the development of new analytical frameworks, the nature of these frameworks, and the empirical studies that sprouted from them.