This article uses social network and spatial data from the National Longitudinal Study of Adolescent Health (Add Health) to examine the effect of racial residential segregation on school friendship segregation in the United States. The use of hierarchical models allows the authors to simultaneously estimate the effects of race, within-school residential segregation, and school diversity on friendship choice using the Add Health data. The authors use these results to predict the decline in friendship segregation that would occur if across- and within-school residential segregation were eliminated in U.S. metropolitan areas. The results suggest that about a third of the level of racial friendship segregation in schools is attributable to residential segregation. Most of this effect is the result of residential segregation across schools rather than within them
