Matsuyama’s main fields of research are international trade and macroeconomics.[8] His thesis for a BA in international relations at the University of Tokyo was on foreign direct investment and multinational corporations. He wrote his doctoral dissertation at Harvard University on the intertemporal approach to the current account and the game-theoretic analysis of the political economy of international monetary policy coordination and of trade and industrial policies. After joining the Northwestern faculty, he has worked extensively on such topics as international trade, , , , , and . He is, in his own words, “interested in understanding the mechanisms behind macroeconomic instability, structural transformation, as well as inequality across countries, regions, and households, and how they interact with credit market imperfections and product market innovations.”[9]