State-Level Changes in Firearm Laws and Workplace Homicide Rates: United States, 2011 to 2017.

To test whether year-over-year strengthening of state-level firearm laws is associated with decreases in workplace homicide rates. In this time-series ecological study of working people in all 50 US states, we used federal data on workplace homicides by state and year from 2011 to 2017, linked to an index of state-year firearm laws, to characterize the regulatory environment (overall and within legislative categories). We used generalized linear regression to model associations between changes in firearm laws and changes in workplace homicide rates the following year. From 2011 to 2017, more than 3000 people died as a result of workplace homicides; over that period, 23 states strengthened firearm regulations and 23 weakened them. We modeled the impact of states strengthening laws within the interquartile range (IQR; equivalent to adding 20.5 firearm laws). This change was associated with a 3.7% reduction in the workplace homicide rate (95% confidence interval [CI] = -3.86, -3.51). Positive IQR changes in specific categories of firearm laws-concealed carry permitting (-5.79%; 95% CI = -6.09, -3.51), domestic violence-related restrictions (-5.31%; 95% CI = -5.57, -5.05), and background checks (-5.07%; 95% CI = -5.32, -4.82)-were also associated with significant reductions. Strengthening state-level firearm laws may reduce the population-level mortality and morbidity burden posed by workplace homicides.