Handgun Acquisitions in California After Two Mass Shootings

Ann Intern Med. 2017 May 16;166(10):698-706. doi: 10.7326/M16-1574. Epub 2017 May 2.


Background: Mass shootings are common in the United States. They are the most visible form of firearm violence. Their effect on personal decisions to purchase firearms is not well-understood.

Objective: To determine changes in handgun acquisition patterns after the mass shootings in Newtown, Connecticut, in 2012 and San Bernardino, California, in 2015.

Design: Time-series analysis using seasonal autoregressive integrated moving-average (SARIMA) models.

Setting: California.

Population: Adults who acquired handguns between 2007 and 2016.

Measurements: Excess handgun acquisitions (defined as the difference between actual and expected acquisitions) in the 6-week and 12-week periods after each shooting, overall and within subgroups of acquirers.

Results: In the 6 weeks after the Newtown and San Bernardino shootings, there were 25 705 (95% prediction interval, 17 411 to 32 788) and 27 413 (prediction interval, 15 188 to 37 734) excess acquisitions, respectively, representing increases of 53% (95% CI, 30% to 80%) and 41% (CI, 19% to 68%) over expected volume. Large increases in acquisitions occurred among white and Hispanic persons, but not among black persons, and among persons with no record of having previously acquired a handgun. After the San Bernardino shootings, acquisition rates increased by 85% among residents of that city and adjacent neighborhoods, compared with 35% elsewhere in California.

Limitations: The data relate to handguns in 1 state. The statistical analysis cannot establish causality.

Conclusion: Large increases in handgun acquisitions occurred after these 2 mass shootings. The spikes were short-lived and accounted for less than 10% of annual handgun acquisitions statewide. Further research should examine whether repeated shocks of this kind lead to substantial increases in the prevalence of firearm ownership.

Primary funding source: None.

MeSH terms

  • Adult
  • Aged
  • California / epidemiology
  • Ethnicity
  • Female
  • Firearms / statistics & numerical data*
  • Humans
  • Male
  • Mass Casualty Incidents*
  • Middle Aged
  • Racial Groups
  • Sex Factors
  • Time Factors