“…They are also grateful for valuable comments from two anonymous referees and from seminar participants at the UK Public Economics Working Group, University of Birmingham, Dartmouth College, University of Maine, Texas A&M University, and University of Warwick. Lucas (1988Lucas ( , 1993, Lord (1989), Becker et al (1990), King and Rebelo (1990), Davies and Whalley (1991), Tamura (1991), Ehrlich and Lui (1991), Jones and Manuelli (1992), Ravikumar (1992, 1997), Nerlove et al (1993), Mulligan and Sala-i-Martin (1993), Caballé and Santos (1993), Barro and Sala-i-Martin (1995), De Gregorio (1996), Mino (1996), Dupor et al (1996), Kaplow (1996), Steurle (1996), Agell and Lommerud (1997), Perroni (1997), Heckman et al (1998), Lin (1998), Lord and Rangazas (1998), Kim (1998), and Heckman (2000).…”