Laws related to the sale, use, and carrying of firearms have been associated with differences in firearm homicide rates at the state level. Right-to-carry (RTC) and stand your ground (SYG) laws are associated with increases in firearm homicide; permit-to-purchase (PTP) laws and those prohibiting individuals convicted of violent misdemeanors (VM) have been associated with decreases in firearm homicide. Evidence for the effect of comprehensive background checks (CBC) not tied to PTP is inconclusive. Because firearm homicide tends to concentrate in urban areas, this study was designed to test the effects of firearm laws on homicide in large, urban U.S. counties. We conducted a longitudinal study using an interrupted time series design to evaluate the effect of firearm laws on homicide in large, urban U.S. counties from 1984 to 2015 (N = 136). We used mixed effects Poisson regression models with random intercepts for counties and year fixed effects to account for national trends. Models also included county and state characteristics associated with violence. Homicide was stratified by firearm versus all other methods to test for specificity of the laws' effects. PTP laws were associated with a 14% reduction in firearm homicide in large, urban counties (IRR = 0.86, 95% CI 0.82-0.90). CBC-only, SYG, RTC, and VM laws were all associated with increases in firearm homicide. None of the laws were associated with differences in non-firearm homicide rates. These findings are consistent with prior research at the state level showing PTP laws are associated with decreased firearm homicide. Testing the effects of PTP laws specifically in large, urban counties strengthens available evidence by isolating the effects in the geographic locations in which firearm homicides concentrate.

BackgroundThe mass shooting phenomenon has gained much attention lately as this form of gun violence appears to increase in frequency. Although many organizations collect information on mass shootings (fatal and nonfatal injuries), no federal definition of this phrase exists. The purpose of this study was to highlight the different statistics that result among databases that define and track “mass shootings.” Establishing definitive guidelines for a mass shooting definition could improve research credibility when presenting evidence to policy makers.MethodsWe obtained data for mass shootings that occurred in 2017 from four sources: Gun Violence Archive, Mother Jones Investigation, Everytown for Gun Safety, and FBI’s Supplemental Homicide Report. We also examined FBI’s Active Shooter Report to compare the mass shootings datasets with active shooter situations, which have been federally defined. First, we examined the overlap among databases. Then, we applied the strictest fatal mass shooting definition to the mass shooting datasets to determine whether the differences in databases could be contributing to differences in fatalities and injuries recorded.ResultsGun Violence Archive recorded the most mass shooting incidents at 346 incidents in 2017, while Mother Jones only recorded 11 cases. Only 2 events were found in all four mass shooting datasets. When the strictest definition – four or more individuals fatally shot – was applied to all datasets, the number of mass shootings in 2017 ranged from 24 (Gun Violence Archive) to 5 (Mother Jones), but incidents collected still varied.ConclusionsThere is much variety in statistics obtained from the different sources that have collected mass shooting information, with little overlap among databases. Researchers should advocate for a standard definition that considers both fatalities and nonfatalities to most appropriately convey the burden of mass shootings on gun violence.

Firearms are a leading cause of death and injury in the United States, and this trend has continued during the COVID-19 pandemic. We sought to identify whether states designated gun retailers as essential businesses in their stay-at-home orders and characterize other references that could affect firearm acquisition during the COVID-19 pandemic. In this cross-sectional policy review, we assessed stay-at-home orders issued in March or April 2020. Orders were reviewed in their entirety, and any reference to firearms, firearm retailers, shooting ranges, or other relevant elements was documented. Forty-three states and the District of Columbia issued stay-at-home orders. Most considered federal firearm licensees to be among essential businesses or made provisions for them to remain open during widespread business closures. Others referenced the US Department of Homeland Security's Cybersecurity and Infrastructure Security Agency (CISA) advisory memorandum on essential critical infrastructure workers which named workers supporting firearm manufacturing and retail among essential workers. Therefore, stay-at-home orders issued in most states included provisions for firearms retailers to remain open, at least in some capacity. Only four states and the District of Columbia did not include federal firearms licensees among essential businesses or include provisions for them to be open. Meanwhile, an all-time high in firearm background checks indicates firearm sales have markedly increased. Given the associations between firearm access and injury risk, the effects of continued firearm access facilitated by these orders should be the focus of future research.

The authors would like to publish this erratum to correct estimates generated from regression analyses due to errors discovered in the coding of some state laws. The following corrections to the laws in Table 1 are warranted: 1) Michigan no longer requires a permit-to-purchase for handgun sales by licensed dealers effective December 18, 2012 (permits are still necessary for private transfers); 2) Connecticut enacted a law prohibiting firearm purchases for violent misdemeanants effective October 1, 1994; and 3) the implementation dates for violent misdemeanant prohi