This project aims to evaluate the role of pharmacy benefit managers (PBMs) in drug pricing negotiations, understand the impacts of PBM mergers, and consider policies that improve prescription drug costs for patients using a newly developed model. The project will focus on competition and rebates for two classes of drugs (statins and atypical antipsychotics) before and after PBM acquisitions. Using a previously developed model, the project will estimate three key model factors — drug utilization, plan enrollment, and insurer-PBM negotiations — to understand the role of PBMs in intermediating drug pricing negotiations. The project also will simulate changes to the vertical market structure and policies that regulate PBMs to quantify how PBM regulations impact patients and access. The data sources are Medicare Part D enrollment and claims data from the Centers for Medicare and Medicaid Services, hand-collected records of PBM formularies, and data on drug rebates from SSR Health.