Ethnicity was ascertained by asking participants to check how they would “describe [their] race or ethnicity.” Choices were: White–European American, Black–African American, Latino–Hispanic, Asian American or Pacific Islander, Native American (Indian), or Other. Multiple selections were allowed. If two individuals matched on any checked choice, they were coded as having the same ethnicity. This variable was a dyadic covariate, that is, a (symmetrical) property of pairs of individuals. This approach provides a parsimonious control for ethnicity-based friendship selection in a network model, particularly when ethnic differences are not the focus of the model.
