This empirical analysis updates and broadens the work done by Logan and Schneider on 1960 and 1970 data (Urban Affairs Quarterly, March 1982). In an analysis of 1980 non-central-city/central-city income inequality for 100 SMSAs, it is found in the current study that property tax reliance, annexation history, percentage black, and central-city age are significant factors. The individual parameter estimates of the regression analysis provide empirical support for the political modification of ecological theory put forth in this article, and provide little support for the traditional nonpolitical "ecological" view of residential differentiation. There is partial support for the theory that SMSA municipalities are active agents in influencing residential location patterns, and are not passive reactors to individual economic decisions. Modification of the ecological explanation to include governmental structure and fiscal organization variables will increase the accuracy and policy relevance of research in the field of metropolitan residential differentiation.