The Index of Dissimilarity
The index of dissimilarity measures the differences in the distributions of different population groups (for example, blacks, whites, or members of different nationalities) over census tracts. If the different populations were evenly distributed across all census tracts, there would be no difference in their distributions--the index would be 0. On the other hand, if both groups were located in census tracts that were racially homogenous--if there were no racially integrated areas--their geographic distribution would be completely different. The index of dissimilarity would be 1.0.
Economic Transition: Further Data
This appendix contains detailed analyses of job data developed in summary form in Chapter 2. The depth of the analyses involved would have drawn attention away from the central points of that chapter. At the same time, the materials are important to a full understanding of the economic shifts facing the Philadelphia area. Hence, we provide these materials here for further reference.
The discussion in Chapter 2 of job changes in the Delaware Valley points to the crucial distinction between city and suburbs, and to the different distributions reported at different wage levels. In particular, Table 2.3 and Figure 2.4 are used to support our major conclusions. Although these reflect the general pattern of changes, it should also be noted that these changes did not apply equally across all industries.
Neither the table nor the figure reveals the contributions of each level of earnings to the total amount of change that occurred. In other words, as jobs increased in the suburbs and decreased in the city, what role did