Relative Rate Index (RRI) compares the arrest rate for a particular racial group with the total arrest rate for all juveniles. For example, an RRI of 2.0 means that members of that group are two times more likely to be arrested than the total population. Note that for RRI values less than 1, the data is interpreted as 1 divided by the RRI. For example, an RRI of 0.8 would mean members of that group are 25% less likely (1/0.8=1.25) to be arrested than the total population.
Arrest rates are based on data collected using the National Incident Based Reporting System (NIBRS).
Population data for youth between the ages of 10 and 17, used to calculate the RRI, are retrieved from the National Center for Juvenile Justice's "Easy Access to Juvenile Populations (EZAPOP" data, which can be found here: http://www.ojjdp.gov/ojstatbb/ezapop/
Arrest data for this measure come from the Washington State Governor's Juvenile Justice Advisory Committee (GJJAC) Juvenile Justice Reports. The report notes that GJJAC obtained these arrest data from Washington Uniform Crime Reporting (WUCR) program of the Washington Association of Sheriffs and Police Chiefs.
Data are available online at https://www.dshs.wa.gov/ra/office-juvenile-justice/washington-state-juvenile-justice-annual-report
Data last updated in May 2016 by Washington KIDS COUNT.
The arrest counts used to calculate the RRI may include juveniles under age 10, based on the National Incident Based Reporting System (NIBRS). The number of arrests does not represent every juvenile arrest made during the year, but reflects the information that was reported. Therefore, underreporting is likely. According to GJJAC, these numbers have not been adjusted by subtracting the population of police jurisdictions that did not report arrest data to Washington Uniform Crime Reporting (WUCR). The arrest data do not include runaways or curfew violators reported to WUCR by individual agencies. The GJJAC report also mentions that major underreporting by law enforcement is observed in Spokane. Therefore, the actual number of arrests for Spokane county is greater than the total reported by law enforcement.
Starting in 2013, the Washington Association of Sheriffs and Police Chiefs (WASPC) began reporting using National Incident-Based Reporting System (NIBRS), replacing the UCR system. The methodologies differ significantly and therefore comparison between the two is not recommended.
Racial/ethnic categories are not mutually exclusive. Racial/ethnic proportions include persons of Hispanic origin. Persons of Hispanic origin can be of any race/ethnicity; however, typically in WUCR they are included in the White racial category.
For more information on RRIs and how they should be interpreted, read this report by the Washington State Center for Court Research.