The volume and characteristics of juvenile court caseloads are partly a function of the size and demographic composition of a jurisdiction's population. Therefore, a critical element in the Archive's development of national estimates is the population of youth that generate the juvenile court referrals in each jurisdiction—i.e., the "juvenile" population of every U.S. county.

A survey of the Archive's case-level data shows that very few delinquency or status offense cases involve youth younger than 10. Therefore, the lower age limit of the juvenile population is set at 10 years for all jurisdictions. On the other hand, the upper age limit varies by State. Every State defines an upper age limit for youth who will come under the jurisdiction of the juvenile court if they commit an illegal act. (See "upper age of jurisdiction" in the "Glossary of Terms" section.) Most States define this age to be 17 years, although some States have set the age at 15 or 16. States often enact exceptions to this simple age criterion (e.g., youthful offender legislation and concurrent jurisdiction or extended jurisdiction provisions). In general, however, juvenile courts have responsibility for all law violations committed by youth at or below the upper age of original jurisdiction.

For the purposes of this Report, therefore, the juvenile population is defined as the number of youth living in a jurisdiction who are at least 10 years old but who are not older than the upper age of original juvenile court jurisdiction. For example, in New York, where the upper age of juvenile court jurisdiction is 15, the juvenile population is the number of youth residing in a county who are between the ages of 10 and 15.

The juvenile population estimates used in this Report were developed with data from the Bureau of the Census.¹ The estimates, separated into single-year age groups, reflect the number of whites, blacks, and individuals of other races who reside in each county in the Nation and who are between the ages of 10 and the upper age of original juvenile court jurisdiction.²

U.S. Bureau of the Census. (1994). 1980-1989 Preliminary Estimates of the Population of Counties by Age, Sex, and Race [machine-readable data file]. Washington, DC: U.S. Bureau of the Census.

U.S. Bureau of the Census. (1999). Estimates of the Population of Counties by Age and Gender: 1990–1997 [machine- readable data file]. Washington, DC: U.S. Bureau of the Census.

U.S. Bureau of the Census. (1999). Estimates of the Population of Counties by Age, Sex, and Race/Hispanic Origin: 1990-1997 [machine-readable data file]. Washington, DC: U.S. Bureau of the Census.

2 “Other races” are Asians, American Indians, and Pacific Islanders. Most individuals of Hispanic ancestry are coded as white.