A Method for Studying Differences in Segregation Across Time and Space

An important topic in the study of segregation are comparisons across space and time. This paper extends current approaches in segregation measurement by presenting a five-term decomposition procedure that can be used to understand more clearly why segregation has changed or differs between two comparison points. Two of the five terms account for differences in segregation that are due to the differing marginal distributions (e.g., the gender and occupational distributions), while one term accounts for differences in segregation due the different structure of segregation (what might be termed “pure” segregation). The decomposition thus presents a solution to the problem of margin-dependency, frequently discussed in the segregation literature. Finally, two terms account for the appearance or disappearance of units when analyzing change over time. The method can be further extended to attribute structural changes to individual units, which makes it possible, for instance, to quantify the effect of each occupation on changing gender segregation. The practical advantages of the decomposition are illustrated by two examples: a study of changing occupational gender segregation in the U.S, and a study of changing residential segregation in Brooklyn, New York City.