Strong network ties are associated with positive outcomes — especially when there is a positive, theoretical link between communication quality and those outcomes. The effect of strong ties on outcomes, however, is also often confounded. For example, communities with clear norms may facilitate the formation of strong ties while also promoting the welfare of their members. In this paper we estimate the causal effect of strong ties by examining the quasi-random departure of social actors in a network. We study how the specialty health care that patients receive is a function of the strength of the relationship between the primary care physician (PCP) and the specialist that the PCP refers to. We leverage the departure of specialists — as captured by relocations, retirements and deaths — to estimate how the spending and health outcomes of the patients seen by a PCP vary with shifts in access to strongly tied specialists.