Baltimore Ceasefire 365: Estimated Impact of a Recurring Community-Led Ceasefire on Gun Violence.

Objectives. To estimate the impact of recurring community-led, weekend-long ceasefires on gun violence in the City of Baltimore, Maryland.Methods. The City of Baltimore releases detailed data on all crimes occurring in the city. We compiled daily counts of fatal and nonfatal shootings occurring between January 2012 and July 2019 and fit a Bayesian model to estimate the impact of the ceasefires on gun violence during designated weekends after accounting for yearly seasonality, day of the week, calendar days, and overall time trends. We also looked at the 3-day periods following each 3-day ceasefire weekend to test for a possible postponement effect.Results. There was an estimated 52% (95% credible interval [CI] = 33%, 67%) reduction in gun violence during ceasefire days and no evidence of a postponement effect on either the next 3 days or the next 3-day weekend following each ceasefire weekend (incidence rate ratio = 0.88; 95% CI = 0.72, 1.06).Conclusions. The Baltimore Ceasefire weekends may be an effective short-term intervention for reducing gun violence. Future research should aim to understand the key components and transferability of the intervention.