Spatial de-concentration of fatal and nonfatal firearm violence in Boston, MA, 2007-2021

It is a "law" of criminology that urban crime chronically recurs at the same microplaces (i.e., street segments and intersections). An influential study found high concentrations of firearm violence at microplaces in Boston, MA, from 1980 to 2008. The current study assessed whether this strong spatial concentration has persisted.

Fatal and nonfatal shooting incidents with one or more victims from January 2007 through September 2021 were included, obtained from the Boston Police Department. We matched shootings to the closest microplaces, i.e., intersections and street segments in Boston (n = 32,267). We operationalized spatial concentration as the probability of shootings occurring at the same microplace. We employed a case-only design, with shootings as the units of analysis; the outcome of interest was a binary indicator for whether another shooting in the dataset occurred at the same microplace in the past or future. We used log-linear regression to estimate this outcome as a function of study year.

Annual shootings decreased over the study period, except for a spike in 2020. Spatial concentration of shootings declined from 62% in 2007 to 55% in 2021. We estimated that spatial concentration declined by an average of 1.8% per year [95% CI (-1.1, -3.4), p < 0.001].

This declining trend in the spatial concentration of firearm violence has important implications for place-based interventions and underscores the need to monitor this trend over time. Social media, which reshapes social interactions and is linked to community violence, warrants further study as a potential cause.