title: Insurer market structure and variation in commercial health care spending.
abstract: OBJECTIVE
  To examine the relationship between insurance market structure and health care prices, utilization, and spending.
  
  
  METHODS
  Claims for 37.6 million privately insured employees and their dependents from the Truven Health Market Scan Database in 2009. Measures of insurer market structure derived from Health Leaders Inter study data.
  
  
  METHODS
  Regression models are used to estimate the association between insurance market concentration and health care spending, utilization, and price, adjusting for differences in patient characteristics and other market-level traits.
  
  
  RESULTS
  Insurance market concentration is inversely related to prices and spending, but positively related to utilization. Our results imply that, after adjusting for input price differences, a market with two equal size insurers is associated with 3.9 percent lower medical care spending per capita (p = .002) and 5.0 percent lower prices for health care services relative to one with three equal size insurers (p < .001).
  
  
  CONCLUSIONS
  Greater fragmentation in the insurance market might lead to higher prices and higher spending for care, suggesting some of the gains from insurer competition may be absorbed by higher prices for health care. Greater attention to prices and utilization in the provider market may need to accompany procompetitive insurance market strategies.
authors.affiliation: Department of Health Care Policy, Harvard Medical School, Boston, MA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: McKellar
authors.forename: Sivia
authors.initials: S
authors.lastname: Naimer
authors.forename: Mary B
authors.initials: MB
authors.lastname: Landrum
authors.forename: Teresa B
authors.initials: TB
authors.lastname: Gibson
authors.forename: Amitabh
authors.initials: A
authors.lastname: Chandra
authors.forename: Michael
authors.initials: M
authors.lastname: Chernew
mesh_terms: D003132:Commerce / Q000191:economics*; D005102:Health Expenditures; D062265:Health Insurance Exchanges / Q000191:economics* / Q000458:organization & administration*; D006801:Humans; D014481:United States
keywords: Geographic variation; competition; markets; spending; utilization