His areas of specialization include labor economics, econometrics, and law and economics. He has been the director of the Industrial Relations Section at Princeton University, and director of the Office of Evaluation of the U.S. Department of Labor, a Guggenheim Fellow, and the Benjamin Meeker Visiting Professor at the University of Bristol. He is a recipient of the IZA Prize in Labor Economics, the Mincer Award for Lifetime Achievement of the Society of Labor Economists, and the Karel Englis Medal awarded by the Charles University in Prague.  He is a Fellow of the Econometric Society, the American Academy of Arts and Sciences, the Society of Labor Economics, and he is a Corresponding Fellow of the Royal Society of Edinburgh. He edited the Handbook of Labor Economics and was editor of the American Economic Review and the co-editor of the American Law and Economics Review. He is a past president of the American Economic Association, the American Law and Economic Association, and the Society of Labor Economists. His current research includes the cross-country measurement of wage rates, and many other issues related to the economics of labor markets.