This publication is the final report of the Criminal Justice Base Rate Project.
This report summarizes the Criminal Justice Base Rate Project, which aims to provide general population base rates. To expand the understanding and use of base rates, the authors of this report provided a unifying metric to facilitate understanding of the decentralized and variant nature of the U.S. justice system’s outcomes. This project provides a source of information that can be used to adjust assessment risk levels locally to provide a better and more accurate assessment of an agency’s population as well as underlying information that knits together once siloed and decentralized data sources. By converting units of analyses to the person-level, base rates across systems can be compared and used to assess the impact of programming, policies, practices, and forecast the impact of proposed legislation on a state’s citizens and the populations under supervision. The interactive database, created as the main project deliverable, provides foundational evidence needed to track justice involvement across multiple metrics and allows for a more consequential understanding of evidence-based impacts of justice system reform efforts. Using data gathered from state courts and two national data sets collected to track arrest and prison admission, the authors computed three definitions of system involvement – arrests, charges, and prison admission. To create state base rates, the authors assembled and analyzed several large data sets. The data assembled represented two metrics – numerators and denominators. The numerator represents justice system involvement by an individual in a given state, each year. The denominator provides a calculation of the number of people in the state eligible yearly who committed a crime and had justice system involvement. Using justice system involvement as the numerator, the authors accessed census data to calculate state populations, representing the general population base rate denominator. These base rates were tracked over multiple years.