Variability of Crime Clearance Among Police Agencies

Average crime clearance rates have remained remarkably stable in the United States since the 1980s, despite many advances in investigative technologies or fluctuations in crime. Taking these average trends at face value, some have suggested that this stability indicates that police departments can do little to alter their clearance rates. However, in this study, we find that the average trends mask substantial long-term variation in crime clearance among police agencies. Using group-based trajectory modeling, we test whether large U.S. police departments have reported uniquely different long-term clearance rate trends from 1981 to 2013 and what organizational factors might contribute to different trends. As we discuss, this method has attractive qualities that provide for a more rigorous analysis compared with past comparative work. Our results show diverse levels and patterns of clearance both within individual crime types and across multiple crime types that appear to covary with organizational factors. We explain how finite mixture modeling can advance both quantitative and qualitative research by identifying departmental differences in performance for further study.