Affiliation: | 1. AED Economics, 2120 Fyffe Rd, Ohio State University, Columbus, OH 43220 USA (e‐mail: partridge.27@osu.edu);2. This paper is based on a lecture given at the North American Regional Science Association meetings in November 2009 in San Francisco. I appreciate the numerous comments by an anonymous reviewer that significantly improved the paper. I also thank Alessandra Faggian, Philip Graves, Tom Knapp, Rose Olfert, Mario Polèse, Jordan Rappaport and Dan Rickman for helpful comments. |