title: The Effect of Geographic Units of Analysis on Measuring Geographic Variation in Medical Services Utilization.
abstract: OBJECTIVE
  We aimed to evaluate the effect of geographic units of analysis on measuring geographic variation in medical services utilization. For this purpose, we compared geographic variations in the rates of eight major procedures in administrative units (districts) and new areal units organized based on the actual health care use of the population in Korea.
  
  
  METHODS
  To compare geographic variation in geographic units of analysis, we calculated the age-sex standardized rates of eight major procedures (coronary artery bypass graft surgery, percutaneous transluminal coronary angioplasty, surgery after hip fracture, knee-replacement surgery, caesarean section, hysterectomy, computed tomography scan, and magnetic resonance imaging scan) from the National Health Insurance database in Korea for the 2013 period. Using the coefficient of variation, the extremal quotient, and the systematic component of variation, we measured geographic variation for these eight procedures in districts and new areal units.
  
  
  RESULTS
  Compared with districts, new areal units showed a reduction in geographic variation. Extremal quotients and inter-decile ratios for the eight procedures were lower in new areal units. While the coefficient of variation was lower for most procedures in new areal units, the pattern of change of the systematic component of variation between districts and new areal units differed among procedures.
  
  
  CONCLUSIONS
  Geographic variation in medical service utilization could vary according to the geographic unit of analysis. To determine how geographic characteristics such as population size and number of geographic units affect geographic variation, further studies are needed.
authors: Department of Health Policy and Management, Seoul National University College of Medicine, Seoul, Korea.
authors: Agnus M
authors: AM
authors: Kim
authors: Department of Health Policy and Management, Seoul National University College of Medicine, Seoul, Korea.
authors: Jong Heon
authors: JH
authors: Park
authors: Department of Health Policy and Management, Seoul National University College of Medicine, Seoul, Korea.
authors: Sungchan
authors: S
authors: Kang
authors: Department of Health Policy and Management, Seoul National University College of Medicine, Seoul, Korea.
authors: Kyosang
authors: K
authors: Hwang
authors: Department of Health Policy and Management, Seoul National University College of Medicine, Seoul, Korea.
authors: Taesik
authors: T
authors: Lee
authors: Department of Health Policy and Management, Seoul National University College of Medicine, Seoul, Korea.
authors: Yoon
authors: Y
authors: Kim
mesh_terms: D016208:Databases, Factual; D003695:Delivery of Health Care / Q000706:statistics & numerical data*; D006801:Humans; D009313:National Health Programs; D066150:Organisation for Economic Co-Operation and Development; D056910:Republic of Korea
keywords: Delivery of health care; Small-area analysis; Utilization