Last Wednesday night, Joel Kotkin—a futurist and (sub)urban historian—squared off in a debate against Christopher Leinberger, a developer, consultant and proponent of "walkable urbanism." The topic: "America 2050: What Will We Build." The pair tangled on four key issues: demographics; housing supply &
demand; transport; and density. Kotkin was in hostile territory: a roomful of Manhattan architects and academics belonging to the Forum for Urban Design.