Justice reinvestment involves the use of informed decisionmaking to more effectively and efficiently manage limited criminal justice resources without compromising public safety. Justice reinvestment is a multi-staged, ongoing process that involves the collaboration of officials, policymakers, and other local stakeholders across city, county, and State systems to determine the most cost effective method for using limited criminal justice resources. One of the primary parts of the Justice Reinvestment at the Local Level (JRLL) model is the use of data from various agencies to identify opportunities for increasing criminal justice efficiencies and measuring the impact of reinvestment activities. This brief discusses the value and use of the various types of data which can be used to identify population drivers, quantify cost drivers, guide reinvestment efforts, and ensure sustainability. Information is provided on the five steps involved in the JRLL model: 1) collect and analyze criminal justice data; 2) identify cost-saving public safety strategies; 3) implement cost-saving public safety strategies; 4) document savings and public safety impact; and 5) implement and assess justice reinvestment strategies. Information is also provided on the use of performance measures to monitor the progress of the JRLL process. Figure, tables, notes, references, and worksheet