Background Homicides in Chicago increased 57% from 2015 to 2016. The first half of 2017 was on par with the first half of 2016. However, August, 2017, marked a dramatic, sustained decrease in homicide deaths, with a net decrease of 18% compared to 2016. Objective To examine the differences among homicide victims in Chicago between two distinct time periods in 2017 by victim demographics, location of residence compared to location of fatal injury, and weapon type.

Methods The Illinois Violent Death Reporting System (IVDRS), a statewide surveillance system, collects data from multiple sources, and is the most accurate and timely source of homicide data in Chicago. Using preliminary data from IVDRS, we discovered a sustained decline in homicides beginning in August 2017 and divided cases into two groups, based on date of death: January to July of 2017 and August to December of 2017. Victim demographics, zip code of victim’s residence compared to zip code where the fatal injury occurred (same versus different) and weapon type (firearm versus non-firearm) were analyzed between the two groups using chi-square analysis.

Conclusion There was a significant decrease in the proportion of homicide victims aged 15 to 24 that occurred between August 1-December 31, 2017 compared to January 1-July 31, 2017 (36.4% versus 44.5%, respectively [p<0.05]). More specifically, there was a significant decrease in the proportion of victims aged 15 to 24 years who died by firearm (37.7% versus 47.2%, respectively [p<0.05]).

Policy implications This significant drop in homicides – and in particular, firearm homicides – among 15 to 24 year olds is positive news. However, we do not yet understand the factors that may have precipitated this change. A careful examination of factors associated with this change is needed to inform policies and programs going forward.