title: Relationship between licensing, registration, and other gun sales laws and the source state of crime guns.
abstract: OBJECTIVE
  To determine the association between licensing and registration of firearm sales and an indicator of gun availability to criminals.
  
  
  METHODS
  Tracing data on all crime guns recovered in 25 cities in the United States were used to estimate the relationship between state gun law categories and the proportion of crime guns first sold by in-state gun dealers.
  
  
  RESULTS
  In cities located in states with both mandatory registration and licensing systems (five cities), a mean of 33.7% of crime guns were first sold by in-state gun dealers, compared with 72.7% in cities that had either registration or licensing but not both (seven cities), and 84.2% in cities without registration or licensing (13 cites). Little of the difference between cities with both licensing and registration and cities with neither licensing nor registration was explained by potential confounders. The share of the population near a city that resides in a neighboring state without licensing or registration laws was negatively associated with the outcome.
  
  
  CONCLUSIONS
  States with registration and licensing systems appear to do a better job than other states of keeping guns initially sold within the state from being recovered in crimes. Proximity to states without these laws, however, may limit their impact.
authors.affiliation: Center for Injury Research and Policy, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD 21205-1996, USA. dwebster@jhsph.edu
authors.forename: D W
authors.initials: DW
authors.lastname: Webster
authors.forename: J S
authors.initials: JS
authors.lastname: Vernick
authors.forename: L M
authors.initials: LM
authors.lastname: Hepburn
mesh_terms: D000704:Analysis of Variance; D003415:Crime / Q000706:statistics & numerical data*; D005389:Firearms / Q000331:legislation & jurisprudence*; D006801:Humans; D008004:Licensure; D016014:Linear Models; D014481:United States