title: Decomposing pharmaceutical cost growth in different types of health plans.
abstract: OBJECTIVE
  To decompose pharmaceutical spending growth into price and quantity components and to compare growth across different types of health plans.
  
  
  METHODS
  Retrospective analysis of pharmaceutical claims for active employees of a large national employer from 1996 to 1998, who were enrolled in traditional fee-for-service plans, health maintenance organizations (HMOs), and preferred provider organizations.
  
  
  METHODS
  Outcomes measures included total cost growth, price growth, and quantity growth. Quantity growth was divided into growth in use of existing products and in use of newly introduced products. For existing products, quantity growth was further decomposed into growth in the number of prescriptions and change in the mix of prescriptions.
  
  
  RESULTS
  During the study period, HMOs had the greatest cost growth. This differential cost growth was largely attributable to changes in utilization as opposed to changes in prices, which were similar among types of health plans. Introduction of new products contributed 15 to 20 percentage points to cost growth in each setting. Differences in cost growth were largely attributed to differences in the growth rate of spending on existing products. For existing products, the impact of increases in the number of prescriptions was much greater in the HMOs, while the impact of changes in the mix of prescriptions was only mildly greater in the HMOs.
  
  
  CONCLUSIONS
  Pharmaceutical cost growth was largely attributable to changes in utilization as opposed to changes in prices. Changes in utilization patterns were complex and differed across types of health plans.
authors.affiliation: Department of Health Management and Policy, University of Michigan School of Public Health, 109 Observatory Rm M3118, Ann Arbor, MI 48109-2029, USA. mchernew@umich.edu
authors.forename: M E
authors.initials: ME
authors.lastname: Chernew
authors.forename: D G
authors.initials: DG
authors.lastname: Smith
authors.forename: D M
authors.initials: DM
authors.lastname: Kirking
authors.forename: A M
authors.initials: AM
authors.lastname: Fendrick
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016527:Drug Costs / Q000639:trends*; D004363:Drug Utilization / Q000191:economics; D017723:Drug Utilization Review; D018588:Fee-for-Service Plans / Q000191:economics*; D005102:Health Expenditures / Q000639:trends*; D006279:Health Maintenance Organizations / Q000191:economics*; D006801:Humans; D008875:Middle Aged; D011243:Preferred Provider Organizations / Q000191:economics*; D012189:Retrospective Studies; D014481:United States