Country-of-birth data contained in registers are often aggregated to create broad ancestry group categories. We examine how measures of residential segregation vary according to levels of aggregation.
We use Swedish register data to calculate pairwise dissimilarity indices from 1990 to 2012 for ancestry groups defined at four nested levels of aggregation: (1) micro-groups containing 50 categories, (2) meso-groups containing 16 categories, (3) macro-groups containing six categories and (4) a broad Western/non-Western binary.
We find variation in segregation levels between ancestry groups that is obscured by data aggregation.
This study demonstrates that the practice of aggregating country-of-birth statistics in register data can hinder the ability to identify highly segregated groups and therefore design effective policy to remedy both intergroup and intergenerational inequalities.