What do arrest statistics count?
To interpret the material in this Bulletin properly, the reader must have a clear understanding of what these statistics count. The arrest statistics report the number of arrests made by law enforcement agencies in a particular year -- not the number of individuals arrested, nor the number of crimes committed. The number of arrests is not equivalent to the number of people arrested because an unknown number of individuals are arrested more than once in the year. Nor do arrest statistics represent counts of crimes committed by arrested individuals, because a series of crimes committed by one individual may culminate in a single arrest or a single crime may result in the arrest of more than one person. This latter situation, many arrests resulting from one crime, is relatively common in juvenile law-violating behavior, because juveniles are more likely than adults to commit crimes in groups. This is the primary reason why arrest statistics should not be used to indicate the relative proportion of crime committed by juveniles and adults. Arrest statistics are most appropriately a measure of flow into the criminal and juvenile justice systems.
Arrest statistics also have limitations in measuring the volume of arrests for a particular offense. Under the UCR Program, the FBI requires law enforcement agencies to classify an arrest by the most serious offense charged in that arrest. For example, the arrest of a youth charged with aggravated assault and possession of a controlled substance would be reported to the FBI as an arrest for aggravated assault. Therefore, when arrest statistics show that law enforcement agencies made an estimated 220,700 arrests of young people for drug abuse violations in 1997, it means that a drug abuse violation was the most serious charge in these 220,700 arrests. An unknown number of additional arrests in 1997 included a drug charge as a lesser offense.