Alan Krueger was one of the most prolific and influential economists of his generation. While his research extended into many different areas, including environmental economics,macroeconomics, and behavioral economics, he identifiedfirst and foremost as a “labor economist.”Hewas a labor economist par excellence, always pushing the field in a new (or long overlooked) direction while maintaining the highest standards for the quality and credibility of his empirical findings. The papers in this issue, written by his students and colleagues in labor economics, pay tribute to some of his major contributions to our field. Virtually every paper builds on one or more of Alan’s ideas. Alan earned his bachelor’s degree in industrial and labor relations from Cornell in 1983. His early education included classes in labor economics and statistics that informed his work throughout his career, including a deep appreciation of the value of original data. Thiswas reflected in the surveys at the heart of many of his best-known papers—including his studies of minimum wages (Katz and Krueger 1992; Card and Krueger 1994), twins (Ashenfelter and Krueger 1994), well-being (Kahneman et al. 2004), and wage posting (Hall and Krueger 2012)—and by his founding of the Survey Research Center at Princeton in 1993. Alan’s 1987 dissertation at Harvard focused on wage determination—a topic he returned to often. The first chapter, which was his job market paper and was later published in theQuarterly Journal of Economics (Krueger 1991), is remarkable for the bold simplicity of its design. Alan proposed to

We employ a revealed preference test to distinguish between wage posting and wage bargaining. Using a sample of dual jobholders in Washington State, we estimate the sensitivity of wages and separation rates to wage shocks in a secondary job. In lower parts of the wage distribution, improvements in the outside option lead to higher separations rates but not to higher wages, consistent with wage posting. In the highest wage quartile, improved outside options translate to higher wages but not higher separation rates, consistent with bargaining. In the aggregate, bargaining appears to be a limited determinant of wage setting.