title: Physician Competition in the Era of Accountable Care Organizations.
abstract: To calculate physician concentration levels for all U.S. markets using detailed data on integration and accountable care organization (ACO) participation.
  
  
  
  2015 SK&A office-based physician survey linked to all commercial and public payer ACOs.
  
  
  
  We construct three separate Herfindahl-Hirschman Index (HHI) measures and plot their distributions. We then investigate how prevailing levels of concentration change when incorporating more detailed organizational features into the HHI measure.
  
  
  
  Horizontal and vertical integration strongly influences measures of physician concentration; however, ACOs have limited impact overall. ACOs are often present in competitive markets, and only in a minority of these markets do ACOs substantively increase physician concentration.
  
  
  
  Monitoring ACO effects on physician competition will likely have to proceed on a case-by-case basis.
authors.affiliation: Department of Health Policy, School of Medicine, Vanderbilt University, Nashville, TN.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Richards
authors.affiliation: Department of Health Policy, School of Medicine, Vanderbilt University, Nashville, TN.
authors.forename: Catherine T
authors.initials: CT
authors.lastname: Smith
authors.affiliation: Department of Urologic Surgery, School of Medicine, Vanderbilt University, Nashville, TN.
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Graves
authors.affiliation: Department of Health Policy, School of Medicine, Vanderbilt University, Nashville, TN.
authors.forename: Melinda B
authors.initials: MB
authors.lastname: Buntin
authors.affiliation: Departments of Urologic Surgery and Health Policy, Center for Surgical Quality and Outcomes Research, School of Medicine, Vanderbilt University, Nashville, TN.|Geriatric Research and Education Center, Tennessee Valley Veterans Affairs Health Care System, Nashville, TN.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Resnick
mesh_terms: D060866:Accountable Care Organizations / Q000458:organization & administration* / Q000706:statistics & numerical data*; D004465:Economic Competition / Q000706:statistics & numerical data*; D006801:Humans; D008511:Medicine / Q000706:statistics & numerical data; D010820:Physicians / Q000706:statistics & numerical data*; D011320:Primary Health Care / Q000706:statistics & numerical data; D018511:Systems Integration; D014481:United States
keywords: Physician markets; accountable care organizations; physician competition; physician consolidation; physician integration