Macartan Humphreys (Ph.D. Harvard) is a Professor of Political Science at Columbia University where he teaches game theory, formal political theory, and the political economy of development. Recent work has appeared in the American Political Science Review , World Politics , and The Economic Journal . He has authored or coauthored books and articles on game theory and politics, ethnic politics, and natural resource management. His most recent book is Coethnicity: Diversity and the Dilemmas of Collective Action .