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152 A time-series study of firearm purchasing following mass shooting events in the us
  1. Gina Liu,
  2. Douglas Wiebe
  1. US University of Pennsylvania


Statement of Purpose Increases in gun acquisitions have been observed following major events, such as select mass shootings and presidential elections. We examined all major mass shootings in the US over the past two decades, to identify events and their characteristics that may affect gun purchasing.

Methods/Approach Data on all background checks for firearm purchases between 1998–2016 were obtained from the National Instant Criminal Background Check System and arrayed as a monthly time series. We also identified all mass shootings with ≥5 victims over the study period. Interrupted ARIMA modelling, considering various lags and decays to optimally fit the pattern and timing of interruptions, was used to identify those events associated (p<0.10) with concurrent changes in gun purchase volume. Then, logistic regression was used to identify demographic, firearm-related, and event-specific characteristics of those mass shootings that evidently impacted gun purchasing.

Results 119 mass shootings and 233,996,385 background checks occurred over the study period. 28 mass shooting events evidently impacted total gun purchases, 25 impacted handgun purchases, and 23 impacted long gun purchases. The most common interruption pattern was an immediate, temporary increase in gun purchases that decayed over 5 months. Only 22 mass shootings led to a decrease in gun purchasing. Only 2 of the 8 characteristics examined – shootings that involved exclusively long guns or received extensive media coverage – were found to be associated with handgun purchasing increases.

Conclusions 41% of recent mass shootings led to changes, typically increases, in gun purchasing in the US Reasons for these increases, which may relate to media coverage and shooters using long guns, are not clear and, if understood, might be used to stabilise gun purchase behaviour.

Significance/Contributions to Injury and Violence Prevention Science Finding that gun purchasing often increases after mass shootings occur could guide public health planning regarding firearms.

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