My specialty is development economics (the study of the economies of poor countries), and I have longstanding interests in: saving behavior and capital markets, especially when willingness-to-pay is a constraint; agriculture; public finance; international commodity markets; and health. My current research projects include a behavioral analysis of infectious diseases based on rational choice; taxation in poor countries, especially the interaction between taxation and the size distribution of firms; and civil wars, especially in Africa. I have traveled widely in Africa and Asia as an economic researcher and adviser, and have been a consultant to the World Bank, the International Monetary Fund, the United Nations Development Program, the Asian Development Bank and other organizations. From 1992 to 1994 I was the editor of The World Bank Research Observer and of The World Bank Economic Review. Before coming to Hopkins, I was Professor of Economics and the Director of the Center for Research on Economic Development (CRED) at the University of Michigan, Ann Arbor.

"The Economical Control of Infectious Diseases," with J. S. Hammer, The Economic Journal, vol. 114, no. 492 (2004), pp. 1-27.

"Infectious Diseases, Public Policy, and the Marriage of Economics and Epidemiology," with J. S. Hammer, The World Bank Research Observer, vol. 18, no. 2 (2003), pp. 129-157.

"Births, Recoveries, Vaccinations and Externalities," in Economics for an Imperfect World: Essays in Honor of Joseph E. Stiglitz eds., R. J. Arnott, et al (Cambridge: MIT, 2003), pp. 469-483.

"Economic Development and the Art of Maintenance," in Development, Duality and the International Regime: Essays in Honor of Gustav Ranis, eds. G. Saxonhouse and T. N. Srinivasan (Ann Arbor: University of Michigan Press, 1999), pp. 244-261.

"The Balance of Self-Reported Heterosexual Activity in KAP Surveys and the AIDS Epidemic in Africa," with H. Jacoby, T. Goze and D. Seri, Journal of the American Statistical Association, vol. 93 (September 1998), pp. 875-883.

"Savings and Nutrition at Low Incomes," Journal of Political Economy, vol. 91, no. 5 (October 1983), pp. 841-855.

"Debt with Potential Repudiation: Theoretical and Empirical Analysis," with J. Eaton, Review of Economic Studies, vol. 48, no. 152 (April 1981), pp. 289-309. Reprinted in Bird, G. and P. N. Snowden, International Debt, vol. 1 (Cheltenham: Elgar, 1995) pp. 56-74.