Table 2.

Network effects included in the model.

Network effects	Definition	Variable type
Outdegree	Ties leaving an actor (number of people marked as friends). Measure of the level of activity in the network.	Control
Reciprocity	Reciprocity is the extent to which ties are reciprocated between actors. Over time if A selects B, then B will reciprocate and select A, or A will drop his/her ties to B. There is an equilibrium tendency toward dyadic relationships to be either reciprocated or null.	Control
Closure (transitive ties and 3 cycles)	The tendency for a friend of a friend to become a friend.	Control
Similarity	Actors tend to form relationships with others who are similar to them in particular ways. Also termed homophily effect or more colloquially known as the idea that “birds of a feather flock together.”	Primary outcome