Firearm laws and illegal firearm flow between US states

Interstate Highway Connections and Traced Gun Transfers Between the 48 Contiguous United States

Importance

Interstate gun flow has critical implications for gun violence prevention, as gun transfers across state lines can undermine local gun control policies.

Objective

To identify possible gun trafficking routes along interstate highways in the US.

Design, Setting, and Participants

This repeated-measures, ecological, cross-sectional study used data from the Bureau of Alcohol, Tobacco, Firearms and Explosives from January 1, 2010, to December 31, 2019, to examine associations between interstate connections via 13 highways that each spanned at least 1000 miles and interstate traced gun transfer counts for the 48 contiguous United States. Analyses were completed in November 2023.

Exposures

Characteristics of the origin states and the transportation connections between the destination state and the origin states.

Main Outcomes and Measures

The main outcome was the total count of guns used in crimes in each destination state per year that were originally purchased in the origin state. Bayesian conditional autoregressive Poisson models were used to examine associations between the count of guns used in crime traced to interstate purchases and interstate highway connections between origin and destination states.

Results

Between 2010 and 2019, 526 801 guns used in crimes in the contiguous 48 states were traced to interstate purchases. Northbound gun transfers along the Interstate 95 corridor were greater than expected to New Jersey (incidence rate ratio [IRR], 2.80; 95% credible interval [CrI], 1.01-7.68) and Maryland (IRR, 3.07; 95% CrI, 1.09-8.61); transfers were similarly greater along Interstate 15 southbound, Interstate 25 southbound, Interstate 35 southbound, Interstate 75 northbound and southbound, Interstate 10 westbound, and Interstate 20 eastbound and westbound.

Conclusions and Relevance

This repeated-measures, ecological, cross-sectional study identified that guns used in crimes traced to interstate purchases moved routinely between states along multiple major transportation routes. Interstate gun transfers are a major contributor to gun crime, injury, and death in the US. National policies and interstate cooperation are needed to address this issue.

Impact of Medicaid Expansion and Firearm Legislation on Cost of Firearm Injuries

INTRODUCTION

Firearm injury-related hospitalizations in the U.S. cost $900 million annually. Before the Affordable Care Act, government insurance programs covered 41% of the costs. This study describes the impact of Affordable Care Act Medicaid expansion and state-level firearm legislation on coverage and costs for firearm injuries.

METHODS

This cross-sectional study included 35,854,586 hospitalizations from 27 states in 2013 and 2016. Data analyses were performed in 2022. Firearm injuries were classified by mechanism: assault, unintentional, self-harm, or undetermined. The impact of the Affordable Care Act expansion was determined using difference-in-differences analysis. Differences in per capita costs between states with stronger and weak firearm legislation were compared using univariable and multivariable analyses.

RESULTS

The authors identified 31,451 initial firearm injury-related hospitalizations. In states with weak firearm legislation, hospitalization costs per 100,000 residents were higher from unintentional ($25,834; p=0.04) and self-inflicted ($11,550; p=0.02) injuries; there were no state-level differences in assault or total per capita firearm-related hospitalization costs. Affordable Care Act expansion increased government coverage of costs by 15 percentage points (95% CI=3, 29) and decreased costs to uninsured/self-pay by 14 percentage points (95% CI=6, 21). In 2016, states with weak firearm legislation and no Affordable Care Act expansion had the highest proportion of hospitalization costs attributed to uninsured/self-pay patients (24%, 95% CI=15, 34).

CONCLUSIONS

Affordable Care Act expansion increased government coverage of hospitalizations for firearm injuries. Unintentional and self-harm costs were significantly higher for states with weak firearm legislation. States with weak firearm legislation that did not expand Medicaid had the highest proportion of uninsured/self-pay patients.

Associations between Gun Ownership and Firearm Homicide Rates in US States

The United States combine high rates of firearm homicides with high gun prevalence. In the past, a significant positive association was found between the two. This study revisits the gun prevalence-gun homicide debate using more elaborate estimates of gun ownership for the 50 States. Longitudinal data (1999-2016) were analysed with Bayesian multilevel Gamma-Poisson models. The results demonstrated a very small positive association that diminished after adjusting for crime rates. Findings suggest that the association either attenuated in more recent years, or previous studies had overestimated this association.

Gun shows and universal background check laws across state lines

States with more gun laws have fewer gun assaults, and associations are strongest for background check laws. However, sales between private buyers and sellers (i.e., gun shows) are exempt from some background check requirements according to federal and most state laws. The aim of this study was to determine whether gun shows are more likely to take place in counties that are near states with universal background check laws. This cross-sectional study used gun show data from a 2018 public online listing aggregated within 3107 counties in the contiguous 48 states. The main independent variable was the presence of a universal background check law in neighboring states. We controlled for potential drivers of demand for gun shows, including the total number of gun laws within-state and in neighboring states, local and in-flowing population size, and proportion of the local and in-flowing population who were gun owners. Bayesian conditional autoregressive Poisson models estimated associations between neighboring-state universal background check law and the presence of a gun show in each county while accounting for spatial dependencies and nesting of counties within states. Of the 1869 identified gun shows, nine of the states in which they occurred had a universal background check law. The presence of excess gun shows in counties near states with universal background check laws is consistent with the hypothesis that gun shows service demand from people seeking to circumvent prohibitions against gun purchases.

State Firearm Legislation and Youth/Young Adult Handgun Carrying in the United States

PURPOSE

To examine the association between state firearm legislation and youth/young adult handgun carrying in the United States and to identify policy priority areas for intervention.

METHODS

We linked person-level gun carrying data from a nationally representative sample of U.S. youth and young adults with state-level gun policies over a 15-year period. Cross-classified mixed effects logistic regressions estimated the associations between state gun policies and handgun carrying and explored whether the associations varied by person-level demographic characteristics.

RESULTS

Youth and young adults in states with a greater number of gun policies were less likely to carry a handgun than youth and young adults in states with fewer gun policies. Regulations on gun purchasing, concealed carrying permitting, and domestic violence-related laws were particularly important in reducing youth/young adult gun-carrying behavior. In addition, these associations varied by gender and race/ethnicity.

DISCUSSION

State firearm legislation may be an effective mechanism to reduce youth and young adult gun carrying and ultimately mitigate gun-related mortality and morbidity.

A Closer Look at the Rising Epidemic of Mass Shootings in the United States and Its Association With Gun Legislation, Laws, and Sales

INTRODUCTION

Mass shootings pose a considerable threat to public safety and significantly cost the United States in terms of lives and expenses. The following are the specific aims of this study: (1) to assess US mass shootings, firearm-related sales, laws, and regional differences from 2015 to 2021 and (2) to investigate changes in mass shootings and firearm sales before and during the Coronavirus Disease 2019 pandemic.

METHODS

A retrospective review was conducted of mass shootings, gun sales, and laws regarding the minimum age required to purchase a firearm within the United States from 2015 to 2021. The 10 states/regions with the greatest mean mass shootings/capita from 2015 to 2021 were selected for further analysis.

RESULTS

Mass shootings correlated significantly with firearm sales from 2015 to 2021 nationwide (P < 0.02 for all). The growth in mass shootings, the number killed/injured, and gun sales were greater in 2020 and 2021 compared to the years prior. The 10 states with the highest mean mass shooting/capita over the study period were Alabama, Arkansas, the District of Columbia, Illinois, Louisiana, Maryland, Mississippi, Missouri, South Carolina, and Tennessee. No significant correlation was found between the number of mass shootings/capita and the minimum age to purchase a firearm.

CONCLUSIONS

Firearm sales correlated significantly with mass shootings from 2015 to 2021. Mass shootings and gun sales increased at greater rates during the Coronavirus Disease 2019 pandemic compared to the years before the pandemic. Mass shootings exhibited inconsistent trends with state gun laws regarding the minimum age to purchase a firearm. Future studies may consider investigating the methods by which firearms used in mass shootings are obtained to further identify targets for prevention.

What factors drive state firearm law adoption? An application of exponential-family random graph models

Guns are a ubiquitous feature of contemporary US culture, driven, at least partly, by firearms' constitutional enshrinement. However, the majority of laws intended to restrict or expand firearm access and use are formulated and passed in the states, leading to 50 different firearm-related legal environments. To date, little is known about why some states pass more restrictive or permissive firearm laws than others. In this article, we identify patterns of firearm law adoption across states, by framing the problem as a bipartite network (states connected to laws and laws connected to states) that is the result of a complex, and interconnected system of unobserved forces. We employ Exponential-family Random Graph Models (ERGMs), a class of statistical network models that allow for the dispensing of the assumptions of statistical independence, to identify factors that increase or decrease the likelihood of states adopting permissive or restrictive firearms laws over the period 1979 to 2020. Results show that more progressive state governments are associated with a higher chance of enacting restrictive firearm laws, and a lower chance of enacting permissive ones. Conservative state governments are associated with the analogous reversed association. States are more likely to adopt laws if bordering states have also adopted that law. For both restrictive and permissive laws the presence of a law in a neighboring state increased the conditional likelihood of a state having that law, that is laws diffuse across state borders. High levels of homicides are associated with a state having adopted more permissive, but not more restrictive, firearm laws. In summary, these results point to a complex interplay of state internal and external factors that seem to drive different patterns of firearm law adoption Based on these results, future work using related classes of models that take into account the time evolution of the network structure may provide a means to predict the likelihood of future law adoption.

Firearm Homicide Incidence, Within-state Firearm Laws, and Interstate Firearm Laws in US Counties

BACKGROUND

Firearm homicides occur less frequently in US states with more firearm control laws. However, firearms are easily transported across state lines, and laws in one location may affect firearm violence in another. This study examined associations between within-state firearm laws and firearm homicide while accounting for interference from laws in other nearby states.

METHODS

The units of analysis were 3,107 counties in the 48 contiguous US states, arrayed in 15 yearly panels for 2000 to 2014 (n = 46,605). The dependent measure was firearm homicides accessed from the Centers for Disease Control and Prevention (CDC) Compressed Mortality Data. The main independent measures were counts of firearm laws and the proportion of laws within categories (e.g., background checks, child access prevention laws). We calculated these measures for interstate laws using a geographic gravity function between county centroids. Bayesian conditional autoregressive Poisson models related within-state firearm laws and interstate firearm laws to firearm homicides.

RESULTS

There were 172,726 firearm homicides in the included counties over the 15 years. States had between 3 and 100 firearm laws. Within-state firearm laws (incidence rate ratio [IRR] = 0.995, 95% confidence interval [CI] = 0.992, 0.997) and interstate firearm laws (IRR = 0.993, 95% CI = 0.990, 0.996) were independently associated with fewer firearm homicides, and associations for within-state laws were strongest where interstate laws were weakest.

CONCLUSIONS

Additional firearm laws are associated with fewer firearm homicides both within the states where the laws are enacted and elsewhere in the United States. Interference from interstate firearm laws may bias associations for studies of within-state laws and firearm homicide.