Recent trends in urban spatial structure.

Results of an investigation of the existence and significance of employment concentrations outside the central business districts of large metropolitan areas are presented. Trends in the intrametropolitan location of employment during te 1960s and early 1970s are examined by using small-area data for two points in time. The spatial detail of the data is roughly equivalent to that of census tracts. While it is known that cities are becoming multinucleated, studies with sufficient spatial detail to permit observations on alterations in urban subcenters are virtually nonexistent. This study explores those trends. Results are presented as (1) a review of the existing theory of urban subcenters and description of data sources and problems, (2) an examination of patterns of metropolitan deconcentration using traditional density approaches, (3) an application of an index of noncentral concentration derived from Lorenz curves measuring noncentrally focused spatial concentration, (4) a cartographic analysis of absolute changes in employment levels over the period of record for each city to identify employment growth centers outside the city center, and (5) an analysis of employment subcenters - their composition and transition - as a tool in delineating the process by which subcenters develop. 6 figures, 4 tables. (SAC)