The assessment found that from approximately 1984 to 1994, the arrest and incarceration of offenders between the ages of 18 and 25 had increased dramatically nationwide. Although there are no accurate data on the number of STG and street-gang members in correctional facilities, many correctional administrators and staff assigned to monitor STGs and street gangs report that this age group of offenders is composed mostly of street-gang members involved in drug dealing linked to violent crimes. These gang members seek to continue the use of violence in controlling drug smuggling from outside into prisons and jails. In response to this trend, prison and jail administrators have begun to create special units to monitor and track the growth of STGs and street gangs among their inmates. The Maricopa County Sheriff's Office (Arizona), for example, established a Jail Intelligence Unit, which collects and analyzes intelligence on STGs. This involves developing confidential sources, conducting mail scans, monitoring inmate phone calls, and identifying STG and street-gang members when they are booked into the facility. The unit is instrumental in developing jail security and safety policies. The prevention of several major incidents in Maricopa County jails has been attributed to the work of the Jail Intelligence Unit.