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Summary. We test the null hypothesis that municipalities defined as central cities by the US Bureau of the Census in 1990 are homogeneous-a hypothesis we reject. Rather, we find that US central cities consist of 2 distinct subsets of municipalities that are aggregated from 13 cluster groupings. The article has two purposes. The first is methodological. We develop a method that uses cluster analysis to group US central cities; then we employ discriminant analysis to establish the statistical validity of those groups. We also develop techniques to minimise the role of judgement in selecting the appropriate cluster solution. The second purpose of the article is to test the substantive null hypothesis. Our rejection of the homogeneity assumption raises the spectre of specification error in research and public policies that assume homogeneity among central cities.
1. What Does `Central City' Mean?
The power of the term `central city' lies in the image it connotes. Say the word, and an icon of urban America is immediately constructed: large municipalities that are disproportionately poor and distressed, both socially and economically. When the term is used as an image, its use incorporates the functions of America's core municipalities (what is done within central cities) their conditions (or the social and economic outcomes from those functions that are disproportionately concentrated in stereotypical central cities), and the physical structure of stereotypical American metropolitan areas (a core central city dominated by poor residential neighbourhoods surrounded by wealthier suburbs). This image is based largely on older central cities, most often located in the north-east and midwest US. A central city is typified as being the primary municipality of an expansive metropolitan area, consisting of a dense and dominant central business district surrounded by enclaves of the poor that often overlap with minority residential neighbourhoods.
Although that image is powerful, it does not apply equally well to all central cities in the nation. Most observers will agree-and much research attests to the fact-that not all US central cities are the same (Bradbury et al., 1982; James, 1990; Ladd and Yinger, 1989; Rusk, 1993; and Wolman et al., 1994). Yet we frequently act as if they are, both in our research and in policy formulations. The reason this heterogeneous set of places tends to...