title: Accountable Care Organizations in the United States: market and demographic factors associated with formation.
abstract: BACKGROUND
  The Accountable Care Organization (ACO) model is rapidly being implemented by Medicare, private payers, and states, but little is known about the scope of ACO implementation.
  
  
  OBJECTIVE
  To determine the number of accountable care organizations in the United States, where they are located, and characteristics associated with ACO formation.
  Cross-sectional study of all ACOs in the United States as of August 2012. We identified ACOs from multiple sources; documented service locations (practices, clinics, hospitals); and linked service locations to local areas, defined as Dartmouth Atlas hospital service areas. We used multivariate analysis to assess what characteristics were associated with local ACO presence. We examined demographic characteristics (2010 American Community Survey) and health care system characteristics (2010 Medicare fee-for-service claims data).
  
  
  RESULTS
  We identified 227 ACOs located in 27 percent of local areas. Fifty-five percent of the US population resides in these areas. HSA-level characteristics associated with ACO presence include higher performance on quality, higher Medicare per capita spending, fewer primary care physician groups, greater managed care penetration, lower poverty rates, and urban location.
  
  
  CONCLUSIONS
  Much of the US population resides in areas where ACOs have been established. ACO formation has taken place where it may be easier to meet quality and cost targets. Wider adoption of the ACO model may require tailoring to local context.
authors.affiliation: The Dartmouth Institute for Health Policy and Clinical Practice, Geisel School of Medicine, Dartmouth College, Lebanon, NH.
authors.forename: Valerie A
authors.initials: VA
authors.lastname: Lewis
authors.forename: Carrie H
authors.initials: CH
authors.lastname: Colla
authors.forename: Kathleen L
authors.initials: KL
authors.lastname: Carluzzo
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Kler
authors.forename: Elliott S
authors.initials: ES
authors.lastname: Fisher
mesh_terms: D060866:Accountable Care Organizations / Q000706:statistics & numerical data*; D003430:Cross-Sectional Studies; D006801:Humans; D008329:Managed Care Programs / Q000706:statistics & numerical data; D006278:Medicare / Q000706:statistics & numerical data; D058007:Physicians, Primary Care / Q000600:supply & distribution; D011787:Quality of Health Care / Q000706:statistics & numerical data; D012111:Residence Characteristics / Q000706:statistics & numerical data; D012959:Socioeconomic Factors; D014481:United States
keywords: Accountable care organizations; Medicare; delivery of health care; health care costs; health care reform; health policy; incentives in health care