Market Share Matters: Evidence Of Insurer And Provider Bargaining Over Prices

Abstract Proposed mergers among large US health insurers and growing consolidation among providers have renewed concerns about the effects of market concentration on commercial health care prices. Using multipayer claims for physician services provided in office settings, we estimated that-within the same provider groups-insurers with market shares of 15 percent or more (average: 24.5 percent), for example, negotiated prices for office visits that were 21 percent lower than prices negotiated by insurers with shares of less than 5 percent. Analyses stratified by provider market share suggested that insurers require greater market shares to negotiate lower prices from large provider groups than they do when negotiating with smaller provider groups. For example, office visit prices for small practices were $88, $72, and $70, for insurers with market shares of