title: The United States Chiropractic Workforce:  An alternative or complement to primary care?
abstract: BACKGROUND
  In the United States (US) a shortage of primary care physicians has become evident. Other health care providers such as chiropractors might help address some of the nation's primary care needs simply by being located in areas of lesser primary care resources. Therefore, the purpose of this study was to examine the distribution of the chiropractic workforce across the country and compare it to that of primary care physicians.
  
  
  METHODS
  We used nationally representative data to estimate the per 100,000 capita supply of chiropractors and primary care physicians according to the 306 predefined Hospital Referral Regions. Multiple variable Poisson regression was used to examine the influence of population characteristics on the supply of both practitioner-types.
  
  
  RESULTS
  According to these data, there are 74,623 US chiropractors and the per capita supply of chiropractors varies more than 10-fold across the nation. Chiropractors practice in areas with greater supply of primary care physicians (Pearson's correlation 0.17, p-value < 0.001) and appear to be more responsive to market conditions (i.e. more heavily influenced by population characteristics) in regards to practice location than primary care physicians.
  
  
  CONCLUSIONS
  These findings suggest that chiropractors practice in areas of greater primary care physician supply. Therefore chiropractors may be functioning in more complementary roles to primary care as opposed to an alternative point of access.
authors.affiliation: Center for Health Policy Research, The Dartmouth Institute for Health Policy & Clinical Practice, 35 Centerra Parkway, Lebanon, NH, 03766, USA. matthew.a.davis@dartmouth.edu.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Davis
authors.forename: Todd A
authors.initials: TA
authors.lastname: Mackenzie
authors.forename: Ian D
authors.initials: ID
authors.lastname: Coulter
authors.forename: James M
authors.initials: JM
authors.lastname: Whedon
authors.forename: William B
authors.initials: WB
authors.lastname: Weeks