Socio-demographic homogenizing trends within fixed-boundary spatial areas in the United States

Using complete census tract, county, and PMSA analog data with longitudinally fixed (standardized) boundaries for the entire United States in 1980, 1990, and 2000, we investigate potential homogenizing trends within spatial areas hypothesized by Massey and others but contradicted by the theorizing of Florida and others. The results for seven socio-demographic variables show a trend toward increasing similarity in the majority of socio-demographic variables in all types of spatial units examined. However, we observe increasing heterogeneity in some conditions and for some variables, particularly racial/ethnic characteristics and family structure. These findings are consistent with the collective body of prior evidence based on less comprehensive data, suggesting that theories of social change and spatial characteristics may benefit from some degree of theoretical integration in which the circumstances under which homogenization or heterogenization may be most likely are better specified theoretically.