The interaction dimension of segregation: Measurement and evidence from US metro areas.∗

We study the heterogeneity of social interaction profiles among individuals and define the extent of the interaction dimension of segregation. An interaction profile quantifies the probabilities that one individual has to interact with different social groups. It can be inferred, for instance, from observation of social ties through networks data. Heterogeneity is minimal if everybody exhibit the same profile, and is maximal if everybody interacts with only one group. All the in-between configurations can be ordered on the bases of an intuitive principle based on operation that generate mixtures of interaction profiles. We proposes a characterization of the Gini-exposure index to assess heterogeneity in interaction patters in a society. We stress the empirical relevance of the index using information of exposure segregation along ethnic lines across US metro area over the last 35 years.