Using the percentage of arrests that end in conviction as the measure of attrition, the authors found a great deal of variation in attrition rates for robbery and burglary arrests. They found no relationship between this variation and community characteristics such as age, race, and poverty, but high attrition rates seemed to be connected to high overall crime rates and low per-arrest expenditures by the police. The authors conclude that statistics reflecting case-attrition patterns are not a valid basis for comparative evaluation of police departments. They suggest further research to discover other factors to explain the variation in case-attrition rates (e.g., the level and detail of the initial patrol investigation, the collection of physical evidence, and the use of special investigative files, proactive investigative techniques, and reward systems).