National estimates are developed by using the national case-level database, the national court-level database, and the Archive's juvenile population estimates for every U.S. county. "County" was selected as the unit of aggregation because (1) most juvenile court jurisdictions in the United States are concurrent with county boundaries, (2) most data contributed by juvenile courts include the county in which the case was handled, and (3) youth population estimates can be developed at the county level.³

The Archive's national estimates are generated by analyzing the data obtained from its nonprobability sample of juvenile courts and then weighting (multiplying) those cases to represent the number of cases handled by juvenile courts nationwide. The Archive employs an elaborate multivariate weighting procedure that adjusts for a number of factors related to juvenile court caseloads: the court's jurisdictional responsibilities (upper age); the size and demographic composition of the community; the age, sex, and race profile of the youth involved in juvenile court cases; and the offenses charged against the youth.

The basic assumption underlying the estimation procedure is that similar legal and demographic factors shape the volume and characteristics of cases in reporting and nonreporting counties of comparable size and features. The estimation procedure develops independent estimates for the number of petitioned delinquency cases, the number of nonpetitioned delinquency cases, and the number of petitioned status offense cases handled by juvenile courts nationwide. Identical procedures are used to develop all case estimates.

The first step in the estimation procedure is to place all U.S. counties into one of four strata based on the population of youth between the ages of 10 and 17. The lower and upper population limits of the four strata are defined each year so that each stratum contains one-quarter of the national population of youth between the ages of 10 and 17. In each of the four strata, the Archive determines the number of juveniles in three age groups: 10- through 15-year-olds, 16-year-olds, and 17-year-olds. The three age groups are further subdivided into three racial groups: white, black, and other. Thus, juvenile population estimates are developed for nine age-by-race categories in each stratum of counties.

The next step is to identify within each stratum the jurisdictions that contributed to the Archive case-level data consistent with JCS reporting requirements. The national case-level database is summarized to determine within each stratum the number of court cases that involved youth in each of the nine age/race population groups. Case rates (number of cases per 1,000 juveniles in the population) are developed for the nine age/race groups within each of the four strata.

For example, assume that a total of 2,059,000 white youth between the ages of 10 and 15 resided in the stratum 2 counties that reported case-level data to the Archive. If the Archive's case-level database shows that the juvenile courts in these counties handled 40,031 petitioned delinquency cases involving white youth between the ages of 10 and 15, the number of cases per 1,000 white youth ages 10 to 15 for stratum 2 would be 19.4, or:

(40,031/2,059,000) x 1,000 = 19.4

Comparable analyses are then used to establish the stratum 2 case rates for black youth and youth of other races in the same age group (58.8 and 27.2, respectively).

Next, information contained in the national court-level database is introduced, and case rates are adjusted accordingly. First, each court-level statistic is disaggregated into the nine age/race groups. This separation is accomplished by assuming that for each jurisdiction, the relationships among the stratum's nine age/race case rates (developed from the case-level data) are paralleled in the aggregate statistic.

For example, assume that a jurisdiction in stratum 2 with an upper age of 15 processed 600 cases during the year and that this jurisdiction had a juvenile population of 12,000 white youth, 6,000 black youth, and 2,000 youth of other races. The stratum 2 case rates for each racial group in the 10-15 age group would be multiplied by the corresponding population to develop estimates of the proportion of the court's caseload that came from each age/race group, as follows:

White:
(19.4 x 12,000) / [(19.4 x 12,000) + (58.8 x 6,000) + (27.2 x 2,000)] = 0.364

Black:
(58.8 x 6,000) / [(19.4 x 12,000) + (58.8 x 6,000) + (27.2 x 2,000)] = 0.551

Other:
(27.2 x 2,000) / [(19.4 x 12,000) + (58.8 x 6,000) + (27.2 x 2,000)] = 0.085

The jurisdiction's total caseload of 600 would then be allocated based on these proportions. In this example, 36.4% of all cases reported in the jurisdiction's aggregate statistics involved white youth, 55.1% involved black youth, and the remaining 8.5% involved youth of other races. When these proportions are applied to a reported aggregate statistic of 600 cases, this jurisdiction is estimated to have handled 218 white youth, 331 black youth, and 51 youth of other races age 15 or younger. The same method is used to develop case counts for all nine age/race groups for each jurisdiction reporting only aggregate court-level statistics.

The disaggregated court-level counts are added to the counts developed from case-level data to produce an estimate of the number of cases involving each of the nine age/race groups handled by reporting courts in each of the four strata. The juvenile population figures for the entire sample are also compiled. Together, the case counts and the juvenile population figures are used to generate a revised set of case rates for each of the nine age/race groups within the four strata.

Stratum estimates for the total number of cases involving each age/race group are then calculated by multiplying the revised case rate for each of the nine age/race groups in a stratum by the corresponding juvenile population in all counties belonging to that stratum (both reporting and nonreporting).

After the national estimate for the total number of cases in each age/race group in each stratum has been calculated, the next step is to generate estimates of their case characteristics. This estimate is accomplished by weighting the individual case-level records stored in the Archive's national case-level database. For example, assume that the Archive generates an estimate of 43,800 petitioned delinquency cases involving white 16-year-olds from stratum 2 juvenile courts. Assume also that the national case-level database for that year contained 17,966 petitioned delinquency cases involving white 16-year-olds from stratum 2 counties. In the Archive's national estimation database, each stratum 2 petitioned delinquency case that involved a white 16-year-old would be weighted by 2.44, because:

43,800/17,966 = 2.44

The final step in the estimation procedure is to impute missing data on individual case records. Table 88 indicates the standardized data elements that were available from each jurisdiction's 1997 data set. The procedures to adjust for missing data assume that case records with missing data are similar in structure to those without missing data. For example, assume that among cases from a particular stratum, detention information was missing on 100 cases involving 16-year-old white males who were petitioned to court, adjudicated for a property offense, and then placed on probation. If similar cases from the same stratum showed that 20% of these cases involved detention, then it would be assumed that 20% of the 100 cases missing detention information also involved detention. Thus, missing data are imputed within each stratum by reviewing the characteristics of cases with similar case attributes (i.e., the age, sex, and race of the youth; the offense charged; and the court's decisions on detention, petition, adjudication, and disposition).

More detailed information about the Archive's national estimation methodology is available upon request from the National Center for Juvenile Justice.