Christopher Snyder is the Joel Z. and Susan Hyatt Professor of Economics at Dartmouth College, where he pursues research and teaching interests in microeconomic theory, industrial organization, and law and economics. He is a research associate in the National Bureau of Economic Research, serves on the board of the Industrial Organization Society, and is an associate editor of the International Journal of Industrial Organization and Review of Industrial Organization. Snyder received his PhD from MIT. His recent research has appeared in leading journals both in and outside economics, including the Journal of Political Economy and Journal of the American Medical Association. He lives in Hanover, New Hampshire, with his wife, who also teaches economics at Dartmouth, and three daughters. Adapting the book for the Europe, Middle East & Africa market for the first time, Robert Stewart is a South African Economics and Econometrics lecturer, researcher and developer based in Johannesburg. Walter Nicholson is the Ward H. Patton Emeritus Professor of Economics at Amherst College and a visiting professor at Ave Maria University, Naples, Florida. Over his teaching career, Professor Nicholson has sought to develop in students an appreciation for the value of economic models in the study of important social questions. He also has enjoyed showing students some of the stranger things that economists have sought to model. Nicholson received his PhD in economics from MIT. Most of his research is in the area of labor economics, especially policy questions related to unemployment.