BRUCE C. N. GREENWALD is the Robert Heilbrunn Professor of Finance and Asset Management at Columbia University Graduate School of Business.JUDD KAHN has taught history, served in city government, and worked as a securities analyst, a CFO, and a management consultant. He has a PhD in history from the University of California, Berkeley.PAUL D. SONKIN is the investment manager of the Hummingbird Value Fund. He has worked at the SEC, Goldman Sachs, Royce Funds, and First Manhattan Company. He holds an MBA from Columbia.MICHAEL van BIEMA is a member of the finance faculty of Columbia Business School. Prior to joining the faculty of Columbia, he was a principal at the RONIN Corporation, a… management consulting firm, and the cofounder of several technology companies. He has a PhD from Columbia in computer science.