Birds of a feather at first sight: Decomposing homophily into tie formation and persistence

Why do some social ties endure while others dissolve? Homophily research typically treats similarity as a single mechanism, conflating processes of tie formation and persistence. I develop a framework based on attribute observability, distinguishing between observable characteristics that guide formation under uncertainty and interaction-revealed attributes that shape tie retention. Using three-wave longitudinal friendship network data and Stochastic Actor-Oriented Models, I decompose homophily into creation and endowment effects across 28 grade networks. Observable attributes (gender, ethnicity) show strong formation effects but little persistence advantage. Interaction-revealed attributes show weaker and less precise patterns. These findings demonstrate that homophily is an information-conditional process and that standard models obscure its underlying mechanisms.