This paper uses newly developed statistical methods to examine the generative processes that give rise to wide-spread patterns in friendship networks. We apply exponential family random graph models to the adolescent friendship networks in fifty-nine US schools from the National Longitudinal Survey of Adolescent Health (Add Health). We model friendship formation as a selection process constrained by individuals’ sociality (propensity to make friends), selective mixing in dyads (friendships within race, grade, or sex categories are more likely), and closure in triads (a friend’s friends are more likely to become friends), given local population composition.

Goodreau, Steven, Kitts, James A., and Martina Morris. “Birds of a Feather or Friend of a Friend? Using Exponential Random Graph Models to Investigate Adolescent Friendship Networks.” Demography, 46(1): 103-126, March 2009.