Designed to reach a wide audience of scholars and policymakers, the "Brookings-Wharton Papers on Urban Affairs" is an annual series that serves as a forum for cutting-edge, accessible research on urban policy. The editors seek to integrate broader research into the policy discussion by bringing urban studies scholars together with economists and researchers studying subjects with important urban implications. "Brookings-Wharton Papers on Urban Affairs" presents new research on urban economics to a broad audience of interested policy analysts and researchers. The papers and comments contained in this volume, the seventh in the series, were presented at a December 8-9, 2005, conference at the Brookings Institution. The papers treat a range of issues examined by contemporary urban economists, including the effects of population growth and changing income inequality on neighborhood segregation, the economic gains from creating express lanes and charging congestion prices on busy expressways, recent trends in the school achievement gap between white and black youngsters, the impact of neighborhood poverty on barriers to employment, the potential benefits of restructuring local property taxes, and the effects of land use restrictions and jurisdictional fragmentation on sprawl and the price of housing. In this issue, six papers on urban economics address a wide range of issues: (1) Metropolitan Growth, Inequality, and Neighborhood Segregation by Income (Tara Watson); (2) Differentiated Road Pricing, Express Lanes, and Carpools: Exploiting Heterogeneous Preferences in Policy Design (Kenneth A. Small, Clifford Winston, and KIA Yarn); (3) Understanding Trends in the Black-White Achievement Gaps during the First Years of School (Richard J. Mundane, John B. Willetta, Kristen L. Bub, and Kathleen McCartney); (4) Neighborhood Effects on Barriers to Employment: Results from a Randomized Housing Mobility Experiment in Baltimore (Kristin Tourney, Susan Clamped-Lundquist, Kathryn Edin, Jeffrey R. Kline, and Greg J. Duncan); (5) Effects of Property Taxation on Development Timing and Density: Policy Perspective (Richard Anett); and (6) Sprawl and Jurisdictional Fragmentation (Edwin S. Mills).