Crime rate is a measure of the rate of occurence of crimes committed in a given area and time. Most commonly, crime rate is given as the number of crimes committed among a given number of persons. Often, the type of crime is exactly specified. Thus, a crime rate might be given as the number of murders (or rapes, thefts, etc.) per 100,000 persons per year within a city.
Crime rate is a useful statistic for many purposes, such as evaluating the effectiveness of crime prevention measures or the relative safety of a particular city or neighborhood. Crime rate statistics are commonly used by politicians to advocate for or against a policy designed to deal with crime. As with any set of statistics, crime rate statistics can be presented in a misleading manner to fit the presenter's agenda.