The second goal of the analyses was to examine the possible determinants of any clustering in alcohol consumption behavior. Three explanations for non-random clustering of alcohol consumption behavior within the network were considered: (1) principals might choose to associate with like contacts (also known as homophily) (23,24); (2) principals and contacts might share attributes or jointly experience unobserved contemporaneous events that cause their alcohol consumption behavior to covary (omitted variables or confounding); and/or (3) contacts might exert social influence or peer effects on principals (induction). Distinguishing the inter-personal induction of drinking from homophily was facilitated by the availability of dynamic, longitudinal data regarding both network connections and drinking behavior (25).
