Compare methods

	Spatial Exposure Index	Index of Dissimilarity
Field	Human Geography	Sociology
Family	Process / pipeline	Process / pipeline
Year of origin	1954	1955
Originator	Wendell Bell (P* indices); Douglas Massey & Nancy Denton (segregation dimensions)	Otis Dudley Duncan & Beverly Duncan
Type	Segregation measure of the potential contact or isolation between population groups	Index of evenness of two groups across units
Seminal source	Bell, W. (1954). A probability model for the measurement of ecological segregation. Social Forces, 32(4), 357–364.	Duncan, O. D., & Duncan, B. (1955). A methodological analysis of segregation indexes. American Sociological Review, 20(2), 210–217.
Aliases	Exposure Index, Isolation Index, P-star Index	dissimilarity index, Duncan index, D index, segregation index
Related	4	5
Summary	The exposure and isolation indices, written P*, measure residential segregation as the degree of potential contact between population groups across the neighbourhoods of a region. Developed by Wendell Bell in 1954 and later codified by Massey and Denton in 1988 as the 'exposure' dimension of segregation, they answer a different question from evenness measures like the dissimilarity index: not how unevenly groups are distributed, but how much members of one group actually share neighbourhoods with members of another or only with their own. The interaction index gauges cross-group exposure while the isolation index gauges within-group concentration, each interpretable as a probability.	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.