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Welcome to my home page. I am Distinguished Professor at the University of Colorado at Boulder, though now retired from the department of economics. My principal interests are in the field of international trade and foreign direct investment. My research for over 45 years has concentrated on the location, production, and welfare effects of large-scale firms and multinational corporations. I am particularly associated with the development of the horizontal approach, in which foreign affiliates replicate many of the activities of other firm establishments in order to serve local and regional markets. On the topic of firm boundaries, my approach focuses on the non-rivaled and non-excludable properties of knowledge capital. Another branch of my work analyzes non-homothetic preferences and explores the role of income elasticities in explaining empirical puzzles. More recently, I am working on exploiting (mathematical) complementarity in general-equilibrium models as a means to endogenize zeros for trade flows, firm types, capacity constraint and choke prices and incomes.

In August 2021, I spent 10 wonderful days in Kyiv, Ukraine. I loved the people and the city. I spend five days teaching a short course on simulation modeling to smart, lively, and focused students from the Ukraine and Georgia. This was followed by several days of celebrations marking the 30th anniversary of Ukraine's independence from the then crumbling Soviet Union. I stand with the people of the Ukraine against Putin's war of terror against a free democratic country and against his own people at home.