"The 2002 National Youth Gang Survey is the eighth annual survey conducted by the National Youth Gang Center (NYGC) since 1995. The 2002 survey used a newly selected sample of law enforcement agencies based on updated data from the U.S. Census Bureau and the Federal Bureau of Investigation. The following local agencies are included in the nationally representative sample: All police departments (n=627) serving cities with a population of 50,000 or more (larger cities). All suburban county police and sheriffs departments (n=745) (suburban counties). A randomly selected sample (n=699) of police departments serving cities with a population between 2,500 and 49,999 (smaller cities). A randomly selected sample (n=492) of rural county police and sheriffs departments (rural counties)."
OJJDP Fact Sheet, No. 01; FS-200401
National Criminal Justice Reference Service (NCJRS): http://www.ncjrs.gov/