Clearance Rates

Uses of Clearance Rates

Clearance rates are useful for several purposes. First, they provide an indication of the risk of committing crimes; that is, it is much easier to get away with committing some crimes than others. The knowledge that police are relatively successful solving certain kinds of offenses can function as a deterrent to those contemplating such actions. Where clearance rates are low, as in the case of auto theft, the message goes out that citizens need to be particularly vigilant and take self-protective measures, such as using steering wheel clubs and alarm systems.

Second, clearance rates are a measure of police productivity—how well the police are doing their job and whether, over time, their performance is improving or declining. Examining the clearance rates of different cities or police precincts within cities is a means of judging the effectiveness of law enforcement in a comparative context. It is especially useful in evaluating special units assigned to particular categories of crimes, such as sex crime units.

Thus, clearance rates are a means of holding police departments and divisions accountable. Reward and punishment of police administrators can be based in part on the objective standard of success in catching criminals rather than intuitions about the quality of their work. Deploying and redeploying of police officers to various locales and responsibilities can also be done more rationally when shortcomings are measured accurately. Clearance rates used in such fashion are part of a standard strategy used by the leadership of modern police departments entailing the use of quantitative data as a management tool (Silverman, 1999).

Problems with Clearance Rates

There are a number of drawbacks in relying on clearance rates, which suggest that they should be interpreted cautiously. First is the issue of accuracy: There is significant potential for error in both the numerator and the denominator of the rate. As to the [Page 68]number of crimes solved (the top of the fraction), the police decision to make an arrest does not mean they have found the right person. Because of mistakes by eyewitnesses, flawed analysis of physical evidence, stereotyping of offenders, and a host of other factors, police sometimes get things wrong. The fact that a significant number of people charged either have their cases dismissed or are acquitted by juries bears this out. It is important to note that exculpation of the charged individual by one means or another does not eliminate the case from the cleared case file and thereby reduce the clearance rate.

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