title: Assessing Differences between Early and Later Adopters of Accountable Care Organizations Using Taxonomic Analysis.
abstract: OBJECTIVE
  To compare early and later adopters of the accountable care organization (ACO) model, using the taxonomy of larger, integrated system; smaller, physician-led; and hybrid ACOs.
  
  
  METHODS
  The National Survey of ACOs, Waves 1 and 2.
  
  
  METHODS
  Cluster analysis using the two-step clustering approach, validated using discriminant analysis. Wave 2 data analyzed separately to assess differences from Wave 1 and then data pooled across waves.
  
  
  RESULTS
  Compared to early ACOs, later adopter ACOs included a greater breadth of provider group types and a greater proportion self-reported as integrated delivery systems. When data from the two time periods were combined, a three-cluster solution similar to the original cluster solution emerged. Of the 251 ACOs, 31.1 percent were larger, integrated system ACOs; 45.0 percent were smaller physician-led ACOs; and 23.9 percent were hybrid ACOs-compared to 40.1 percent, 34.0 percent, and 25.9 percent from Wave 1 clusters, respectively.
  
  
  CONCLUSIONS
  While there are some differences between ACOs formed prior to August 2012 and those formed in the following year, the three-cluster taxonomy appears to best describe the types of ACOs in existence as of July 2013. The updated taxonomy can be used by researchers, policy makers, and health care organizations to support evaluation and continued development of ACOs.
authors.affiliation: Center for Innovation to Implementation, VA Palo Alto Health Care System, Center for Primary Care and Outcomes Research, Stanford University School of Medicine, Menlo Park, CA.
authors.forename: Frances M
authors.initials: FM
authors.lastname: Wu
authors.affiliation: School of Public Health, University of California, Berkeley, Berkeley, CA.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Shortell
authors.affiliation: The Dartmouth Institute for Health Policy and Clinical Practice, Geisel School of Medicine at Dartmouth College, Hanover, NH.
authors.forename: Valerie A
authors.initials: VA
authors.lastname: Lewis
authors.affiliation: The Dartmouth Institute for Health Policy and Clinical Practice, Geisel School of Medicine at Dartmouth College, Hanover, NH.
authors.forename: Carrie H
authors.initials: CH
authors.lastname: Colla
authors.affiliation: The Dartmouth Institute for Health Policy and Clinical Practice, Geisel School of Medicine at Dartmouth College, Hanover, NH.
authors.forename: Elliott S
authors.initials: ES
authors.lastname: Fisher
mesh_terms: D060866:Accountable Care Organizations / Q000458:organization & administration*; D016000:Cluster Analysis; D019033:Delivery of Health Care, Integrated / Q000458:organization & administration*; D006123:Group Practice; D018166:Health Care Reform; D006291:Health Policy; D006801:Humans; D006278:Medicare; D014481:United States
keywords: Accountable Care Organizations; Medicare; delivery of health care; health care reform; health policy