COMMENT.

According to authors, the aim of their work was not to construct a theoretical explanation for the differentiation of urban sub-areas. Duncan herself has indicated that such an explanation would require a longitudinal analysis of areal change. Their research compared a series of empirical regularities that were observed in U.S. cities in 1940 and 1950. In their 1958 report, the bulk of their analysis was concerned with seven generalizations, all of which still stand after researcher Beverly Duncan's comments. Their 1958 report indicated that the generalizations showed less consistency between cities in 1950 than in 1940. While Duncan has implied by her quotations of their 1958 report that these generalizations were a basis for speculation, an explanation of the remainder of the quoted paragraph indicates that the comments were in the form of guidelines for further research, rather than hypotheses or assumptions. Duncan implies that they have confused individual and areal data. A re-reading of both the 1950 and 1958 articles clearly shows that the concern of their research was with population aggregates rather than with individuals.