title: Differing Impacts Of Market Concentration On Affordable Care Act Marketplace Premiums.
abstract: Recent increases in market concentration among health plans, hospitals, and medical groups raise questions about what impact such mergers are having on costs to consumers. We examined the impact of market concentration on the growth of health insurance premiums between 2014 and 2015 in two Affordable Care Act state-based Marketplaces: Covered California and NY State of Health. We measured health plan, hospital, and medical group market concentration using the well-known Herfindahl-Hirschman Index (HHI) and used a multivariate regression model to relate these measures to premium growth. Both states exhibited a positive association between hospital concentration and premium growth and a positive (but not statistically significant) association between medical group concentration and premium growth. Our results for health plan concentration differed between the two states: It was positively associated with premium growth in New York but negatively associated with premium growth in California. The health plan concentration finding in Covered California may be the result of its selectively contracting with health plans.
authors.affiliation: Richard M. Scheffler (rscheff@berkeley.edu) is a distinguished professor at the School of Public Health and the Richard and Rhoda Goldman School of Public Policy, and director of the Nicholas C. Petris Center on Health Care Markets and Consumer Welfare at the School of Public Health, all at the University of California, Berkeley.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Scheffler
authors.affiliation: Daniel R. Arnold is a graduate student researcher at the University of California, Berkeley, and a doctoral student in economics at the University of California, Santa Barbara.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Arnold
authors.affiliation: Brent D. Fulton is an assistant adjunct professor and the associate director of the Nicholas C. Petris Center on Health Care Markets and Consumer Welfare at the School of Public Health, University of California, Berkeley.
authors.forename: Brent D
authors.initials: BD
authors.lastname: Fulton
authors.affiliation: Sherry A. Glied is dean of and a professor of public service at the Robert F. Wagner Graduate School of Public Service at New York University, in New York City.
authors.forename: Sherry A
authors.initials: SA
authors.lastname: Glied
mesh_terms: D000328:Adult; D002140:California; D003365:Costs and Cost Analysis / Q000191:economics*; D004465:Economic Competition / Q000191:economics*; D005260:Female; D006273:Health Facility Merger / Q000191:economics* / Q000458:organization & administration / Q000639:trends; D006801:Humans; D007348:Insurance, Health; D008297:Male; D015233:Models, Statistical; D009518:New York; D058991:Patient Protection and Affordable Care Act / Q000191:economics* / Q000639:trends; D014481:United States
keywords: Health Economics; Hospitals; Insurance Market < Insurance; Physicians