["Econometrica, Volume 94, Issue 3, Page 729-733, May 2026. ", "\nBiopharmaceuticals advance health and economic growth. Unlike central bargaining abroad, the United States uses private firms, pharmacy benefit managers (PBMs), to manage medicine access and spending. Yet, PBMs' roles in advancing efficiency are understudied. Ho and Lee model PBMs' use of tiered formularies, lists of covered medicines, without the use of proprietary data on the price concessions drug makers offer for preferred placement. They find PBMs' use of tiered formularies generate significant payor savings through competition. Complementing Ho and Lee, Feng and Maini (2024) model how patient demand inertia limits PBMs' ability to extract price concessions from drug makers which consequently erodes the efficacy gains of PBM formularies. Conti, Frandsen, Powell, and Rebitzer (2021) model formulary auctions where PBM size drives payor savings, but also spurs endogenously set high list prices, reducing patient access. Future economic research should focus on PBM market entry and vertical integration, pharmacy steering, and effects on innovation.\n"]