Gun violence is a major problem in the United States, and extensive prior work has shown that higher temperatures increase violent behavior. We consider whether restricting the concealed carry of firearms mitigates or exacerbates the effect of temperature on violence. We use two identification strategies that exploit daily variation in temperature and variation in gun control policies between and within states. We provide evidence that more-prohibitive concealed-carry laws attenuate the temperature-homicide relationship. Our findings are consistent with more-prohibitive policy regimes reducing the lethality of altercations.

Gun violence is an important problem across the United States. However, the impact of government policies on gunfire has been difficult to test due to limited and low-quality data. This paper uses new, more accurate data on gunfire (generated by ShotSpotter audio sensors) to measure the effects of juvenile curfews in Washington, DC. Using variation in the hours of the DC curfew, we find that this policy increases gunfire incidents by 150% during marginal hours. In contrast, voluntarily reported crime measures (such as 911 calls) suggest that the curfew decreases gun violence, likely because of confounding effects on reporting rates.

We exploit daylight saving time (DST) as an exogenous shock to daylight, using both the discontinuous nature of the policy and the 2007 extension of DST, to consider the impact of light on criminal activity. Regression discontinuity estimates show a 7% decrease in robberies following the shift to DST. As expected, effects are largest during the hours directly affected by the shift in daylight. We discuss our findings within the context of criminal decision making and labor supply, and estimate that the 2007 DST extension resulted in $59 million in annual social cost savings from avoided robberies.