Insurers’ Negotiating Leverage and the External Effects of Medicare Part D

By influencing the size and bargaining power of private insurers, public subsidization of private health insurance may project effects beyond the subsidized population. We test for such spillovers in Medicare Part D by analyzing how resulting increases in insurer size affected drug prices negotiated in the non-Medicare commercial market. On average, Part D lowered prices for commercial enrollees by 5.3%. The external commercial market savings amount to $2.6 billion per year, which, if passed to consumers, approximates the cost-savings of newly-insured subsidized beneficiaries. If retained by insurers, it corresponds to an 8% average increase in profitability.