Each record consists of identifying details, name, initials, gender, and date of birth; this ID record is matched to produce approximately 6 million criminal histories including type of offense and sentence. The Index yields Janus-type surveys that look both into the past and future. Past work includes tracing the criminal histories of a series of birth cohort samples. The Offenders' Index could become a type of bureau, supplying data files for outside clients who wish to analyze the information. All users must sign a confidentiality statement, agreeing to use the data only for statistical purposes. At present, computing and clerical costs are being studied to produce a costing strategy for both internal and external researchers. 6 appendixes