A Measure of Segregation Based on Social Interactions

We develop an index of segregation based on two premises: (1) a measure of segregation should disaggregate to the level of individuals, and (2) an individual is more segregated the more segregated are the agents with whom she interacts. We present an index which satisfies (1) and (2), and that is based on agents’ social interactions: the extent to which Blacks interact with Blacks, Whites with Whites, etc. We use the index to measure school and residential segregation. Using detailed data on friendship networks, we calculate levels of within-school racial segregation in a sample of US schools. We also calculate residential segregation across major US cities, using block-level data from the 2000 US Census. ∗We are grateful to Gary Becker, Kim Border, Fernando Borraz, Toni Calvo-Armengol, David Card, Joan Esteban, Drew Fudenberg, Edward Glaeser, Jerry Green, Faruk Gul, Oliver Hart, James Heckman, Matthew Jackson, Kevin Lang, Edward Lazear, Erzo Luttmer, Derek Neal, Jesse Shapiro, and two anonymous referees for useful comments and suggestions. We are especially grateful to Lawrence Katz, Glenn Loury, and Kevin Murphy for advice, encouragement, and detailed comments on previous drafts. We thank seminar participants at Berkeley, Boston, Brown, Caltech, Carnegie Mellon, Chicago, Harvard, McGill, NBER, Pompeu Fabra, Torcuato Di Tella, Universitat Autonoma de Barcelona, and Vanderbilt. Katherine Barghaus, Patricia Foo, and Alex Kaufman provided exceptional research assistance. A portion of this paper was written while Fryer was a visitor at Institut d’Anàlisi Económica at Universitat Autonoma in Barcelona, Spain. Fryer gratefully acknowledges financial support from the Alphonse Fletcher Sr. Fellowship.