The effect of historic redlining on firearm violence

Firearm homicides disproportionately affect young Black men, which in turn have lasting impact of communities of color as a whole. Previous cross-sectional studies have highlighted the role of discriminatory housing policies on the incidence of urban firearm violence. We sought to estimate the effects of racist housing policies on firearm incidence.

Firearm incident data were obtained from the Boston Police Department and point locations spatially joined with vector files outlining the original 1930 Home Owner Loan Corporation (HOLC) Redlining maps. A regression discontinuity design was used to assess the increased rate of firearm violence crossing from historically "desirable" neighborhoods (Green) to historically "hazardous" neighborhoods (Red and Yellow) based on HOLC definitions. Linear regression models were fit on either side of the geographic boundaries with firearm incidents graphed at varying distances and the regression coefficient calculated at the boundary.

Crossing from desirable to Red hazardous designation there was a significant discontinuity with an increase of 4.1 firearm incidents per 1,000 people (95% CI 0.68,7.55). Similarly, when crossing from desirable areas to the Yellow hazardous designation there was a significant discontinuity and increase of 5.9 firearm incidents per 1,000 people (95% CI 1.85,9.86). There was no significant discontinuity between the two hazardous HOLC designations (coefficient -0.93, 95% CI -5.71, 3.85).

There is a significant increase in firearm incidents in historically redlined areas of Boston. This suggests that interventions should focus on downstream socioeconomic, demographic, and neighborhood detriments of historically discriminatory housing policies in order to address firearm homicides.