Study
Caplan and colleagues (2021) used a time-series design to examine the effectiveness of the yearlong implementation of the Risk-Based Policing Initiative in Kansas City, Missouri, on reducing violent crime in the intervention areas, compared with the comparison areas. Implementation of the initiative began on March 15, 2019. The pre-intervention period was March 15, 2018, through March 14, 2019. The post-intervention period was March 15, 2019, through March 14, 2020. The estimated population of Kansas City, Missouri, is 495,000 individuals residing across four counties (Cass, Clay, Jackson, and Platte) under the jurisdiction of the Kansas City Police Department (KCPD).
The intervention areas received the Risk-Based Policing Initiative, while the comparison areas received policing as usual.
Intervention areas were selected from maps displaying the highest-risk places and related risk factors diagnosed by risk terrain modeling using RTMDx software, and chronic violent crime hot spots produced by kernel density estimation (KDE)
in ArcGIS. Highest-risk places were defined as places greater than two standard deviations from the mean relative risk score; hot spots were defined as places with KDE values greater than two standard deviations from the mean KDE value (Hart and Zandbergen 2014). Thirteen intervention areas were selected across four (of six) patrol divisions in Kansas City: 1) Central, 2) Metro, 3) East, and 4) South. These patrol divisions cover half of the city’s total land area and accounted for more than 90 percent of violent crimes in the 12 months before the risk-based policing initiative. Between one and four noncontiguous intervention areas were located in each patrol division. The average size of intervention areas within these patrol divisions was 0.38 square miles, with a total coverage area across all divisions of 4.9 square miles, which accounted for 1.5 percent of the city’s land area. The count for violent crimes during the pre-intervention period in the target areas was 1) Central = 166 violent crimes, 2) East = 158 violent crimes, 3) Metro = 210 violent crimes, and 4) South = 178 violent crimes.
Comparison areas were identified at the same time as the intervention areas, based on the same initial set of maps and analytic outputs given to patrol division commanders. Comparison areas were selected if they had qualities similar to the intervention areas in terms of zoning and geographic size. One comparison area was selected in each patrol division. The average size of the comparison areas was 0.85 square miles, with a total coverage of 3.4 square miles, which accounted for 1.1 percent of the city’s land area. The count for violent crimes during the pre-intervention period in the comparison areas was 1) Central = 46 violent crimes, 2) East = 36 violent crimes, 3) Metro = 59 violent crimes, and 4) South = 39 violent crimes.
The outcome of interest was violent crime, which was defined as homicide, aggravated assault, and robbery incidents that involved a weapon. This data were obtained from the KCPD records management system and manually verified by KCPD staff for reliability and validity. The KCPD provided the evaluators with data and details about how the department designated target and comparison areas and how data were used to inform policing activities at the target areas, along with examples pulled from computer-aided dispatch calls for service notes. Target buffer areas were included to assess displacement or diffusion of benefits through a weighted displacement difference test. The ABC spreadsheet calculator version 1.4 (Ratcliffe 2019) was used to assess statistically significant net effects of crime changes in the target areas, compared with the comparison areas. No subgroup analyses were conducted.