Data from the National Criminal Victimization Survey and the FBI's Uniform Crime Report show that the proportion of all property, serious, and violent crimes cleared by arrest of persons under 18 years old continues to be below levels reported in 1972. Based on these clearance data, it appears that juveniles are arrested disproportionately for property offenses but are arrested for violent crimes at rates below the proportion of youth in the Nation's population. Differences between arrest and clearance rates are caused in large part by the greater tendency of juveniles to commit crimes in groups; this distorts the FBI arrest statistics and, therefore, overstates levels of juvenile violence. For instance, information published by the FBI suggests that the younger the offender, the greater the proportion of offenses committed in groups. In 1990 groups composed only of teenagers were responsible for between 35 and 47 percent of all multiple-offender attempted and completed violent crimes of rape, robbery, and assault, a percentage that is more than twice that for offenders in their 20's and six times that for offenders 30 years of age or older. 1 figure