Changes in outlet densities affect violence rates

BACKGROUND: Previous assessments of empirical relationships between alcohol outlets and rates of interpersonal violence have been conducted using cross-sectional spatial data, data collected across small geographic units such as Census Tracts and zip codes. These assessments demonstrate that the availability of alcohol, measured by the number and types of alcohol outlets, is related to violence. These analyses have examined many potential confounds of the outlets-violence connection (i.e., population and place characteristics) and statistically corrected for biases that arise in analyses of spatial data. The current study contributes the first observation of longitudinal relationships between alcohol outlets and violence. METHOD: The study examined longitudinal data from 581 consistently defined zip code areas represented in the California Index Locations Database, a geographic information system that coordinates population and ecological data with spatial attributes for areas across the state. Six years of data were collected on features of local populations (e.g., household size) and places (e.g., retail markets) thought to be related to 1 measure of violence (i.e., hospital discharges related to violent assaults). Assault rates were related to changes in population and place characteristics using random effects models with controls for spatial autocorrelation (n x t = 3,486 observations). Changes in population and place characteristics of bordering (spatial lagged) areas were also considered. RESULTS: Lower median household income and greater percentages of minorities (African American, Hispanic, and Asian) were related to increased rates of violence. Ten percent increases in numbers of off-premise outlets and bars were related to 1.67 and 2.06% increases in violence rates across local and lagged spatial areas. Every 6 outlets accounted for 1 additional violent assault that resulted in at least 1 overnight stay at hospital. These effects increased with larger male populations, doubling with every 3% increase in percent males. CONCLUSION: Assault rates were most strongly related to median household incomes and minority populations within zip code areas. Controlling for changes in assault rates related to these measures, greater numbers of licensed alcohol retail establishments, especially bars and off-premise outlets, were related to rates of assault. Failures to regulate the growth in numbers of bars will increase rates of violence, especially in urban areas.