Geographic Concentration in U.S. Manufacturing Industries: A Dartboard Approach.

This paper discusses the prevalence of Silicon Valley-style localizations of individual manufacturing industries in the United States. A model in which localized industry-specific spillovers, natural advantages, and random chance contribute to geographic concentration motivates new indices of geographic concentration and coagglomeration. The indices contain controls that facilitate cross-industry and cross-country comparisons. The authors find almost all industries to be more concentrated than a random dart-throwing model predicts but the degree of localization is often slight. They also discuss which industries are concentrated, the geographic scope of localization, coagglomeration patterns, and other topics. Copyright 1997 by the University of Chicago.