title: Studying the effects of health plan competition: are available data resources up to the task?
abstract: OBJECTIVE
  To review the availability of data sources to study health plan competition in the United States.
  
  
  METHODS
  The literature on health plan competition was reviewed. Possible data sources to study health plan competition were evaluated. Experts in the field of health plan competition were contacted about their knowledge of existing data sources. Principal Findings. There is much more quantitative data available on HMO plans than on other types of health plans that are growing in popularity, such as PPOs. A key source for health plan data, state health insurance filings, lacks information on beneficiaries in non-HMO plans. Data on health plan quality is growing. In addition, case studies of particular markets is providing useful qualitative information on the dynamics of the health plan industry.
  
  
  CONCLUSIONS
  The fragmentation of the health care market and the hesitancy of governments and private organizations to provide detailed information across markets and providers creates serious obstacles to the study of health plan competition.
authors.affiliation: The MEDSTAT Group, Washington, DC 20008, USA.
authors.forename: T L
authors.initials: TL
authors.lastname: Mark
authors.forename: R M
authors.initials: RM
authors.lastname: Coffey
mesh_terms: D016208:Databases, Factual; D004465:Economic Competition / Q000458:organization & administration*; D019981:Health Care Sector / Q000458:organization & administration / Q000706:statistics & numerical data*; D019538:Health Care Surveys; D006279:Health Maintenance Organizations / Q000191:economics / Q000706:statistics & numerical data; D006302:Health Services Research; D008329:Managed Care Programs / Q000191:economics* / Q000706:statistics & numerical data; D011243:Preferred Provider Organizations / Q000191:economics / Q000706:statistics & numerical data; D014481:United States