He has studied a wide range of subjects in economic theory, such as game theory, the economics of incentives, and contract theory. He is particularly well known for his work on mechanism design/implementation theory and dynamic games. His current research projects include comparing different rules for elections, the causes of inequality and studying coalition formation. He is a Fellow of the "American Academy of Arts and Sciences", "Econometric Society", and the "European Economic Association", and a Corresponding Fellow of the "British Academy". He was president of the "Econometric Society" in 2003.