by Jess Behrens
While with Northwestern University's Medical School, I worked on a project looking at the relationship between gunshot wounds & packaged goods liquor stores. The method involved using the gravity model as described in the FCA 2 Step Method for estimating the probable relationship between a gunshot wound and all of the liquor licenses within the study area. These gravity estimates were then aggregated by census tract and used as an independent variable in an iterative geographically weighted regression (GWR) analysis. The result was to break Chicago into regions or groups of census tracts. Logistic regression was then used to identify the Odds Ratio for liquor licenses within each region.
To ensure that the relationship was not spurious, the process was done repeatedly using multiple business and location types. Schools, churches, grocery stores, etc. were included in the gravity calculations used in this second stage of the analysis. Two comparisons were made: one where the liquor licenses were included with all other business types and a second where only the other business types were included (liquor licenses left out). While risk remained with the liquor licenses included, the risk disappeared when the liquor licenses were dropped.
Of note is the fact that risk was unequal across the study area, and the liquor licenses actually decreased the overall risk of gunshot wounds in some areas. Obviously, the focus was on those areas where the risk significantly increased, but noting this contrary fact is vitally important. The relationship between gunshot wounds and liquor licenses is a complex one that involves multiple social, economic, & spatial dynamics.
Due to publication rules, I can't reproduce the maps and tables here. If you're interested in reading about the study, it has been published in the American Journal of Surgery.
Crandall M, Kucybala K, Behrens J, Schwulst S, Esposito T. Geographic association of liquor licenses and gunshot wounds in Chicago American Journal of Surgery 2015;210(1): 99-105.