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	Spatial Dissimilarity Index	Index of Dissimilarity
Field	Human Geography	Sociology
Family	Process / pipeline	Process / pipeline
Year of origin	1993	1955
Originator	Richard Morrill & David Wong	Otis Dudley Duncan & Beverly Duncan
Type	Boundary-aware index of residential segregation between two groups	Index of evenness of two groups across units
Seminal source	Wong, D. W. S. (1993). Spatial indices of segregation. Urban Studies, 30(3), 559–572.	Duncan, O. D., & Duncan, B. (1955). A methodological analysis of segregation indexes. American Sociological Review, 20(2), 210–217.
Aliases	Spatial Index of Dissimilarity, Adjusted Dissimilarity Index, Boundary-Adjusted Dissimilarity, Spatial Segregation Index	dissimilarity index, Duncan index, D index, segregation index
Related	4	5
Summary	The spatial dissimilarity index is a boundary-aware measure of residential segregation that corrects the classic index of dissimilarity for the fact that areal units are not isolated boxes but neighbours that share borders. Developed by Richard Morrill in 1991 and refined by David Wong in 1993, it discounts the aspatial index by the degree to which adjacent units differ in group composition, so that two groups clustered into separate but neighbouring areas are recorded as less segregated than two groups locked into a checkerboard. It directly addresses the long-standing checkerboard problem that the aspatial Duncan index cannot see.	The index of dissimilarity, often called the Duncan segregation index, measures how unevenly two groups — such as two racial or occupational groups — are distributed across a set of units like neighborhoods, schools, or occupations. It ranges from 0, when both groups have identical distributions across units, to 1, when the units are completely segregated, and has the intuitive interpretation of the share of one group that would have to relocate to achieve an even distribution.