# 2.2.3 Measuring segregation with the Dissimilarity index

Course subject(s) 2. The Vicious Circle of Segregation

The information below is specifically for those who have an interest in the technical aspects of measuring segregation. In the context of this course, it is not necessary to understand the mathematical detail.

The Dissimilarity Index (DI) is used as the main measure of residential segregation between socio-economic groups, reflecting their relative distributions across neighbourhoods within the urban area. Values of DI vary between 0 and 100 (sometimes also referred to as 0 and 1), which indicates the proportion of a group that would need to move in order to create a uniform distribution of population. 0 means that both groups are distributed in the same proportions across all neighbourhoods and 100 means that the members of two groups are located in different neighbourhoods – this is a total segregation. The Dissimilarity Index is calculated as follows: ai is the population of group A in the ith area, e.g. census tract

A is the total population in group A in the large geographic entity for which the index of dissimilarity is being calculated

bi is the population of group B in the ith area

B is the total population in group B in the large geographic entity for which the index of dissimilarity is being calculated 