Some further observations on the index of residential differentiation.

The relationship between the index of residential differentiation (RDI), a recently introduced measure of residential segregation which is designed to summarize the distribution of c social groups in a single index, and the indices of dissimilarity (D) and segregation (SI) is examined. It is demonstrated that RDI is a natural extension of D, and that when c = 2, RDI = D; when c greater than 2, it is possible to stipulate RDI in terms of SI, but it is not possible to stipulate RDI in a straightforward manner in terms of D. An adjusted RDI is then suggested in which random segregation rather than complete desegregation is used as the baseline.