Recent recidivism studies by the AOUSC, USSC, and BJS have brought attention to the importance of understanding the scope of reoffending in the federal probation and pre -trial services system. These studies have also brought to light how difficult it is to compare recidivism rates across agencies. Even when using similar data, discrepancies can exist based on definitional and methodological differences. No study is without error, and any definition will underestimate the “true” recidivism rate, because rates are based on official criminal record data that only show crimes for which people have been arrested or convicted (Blumstein & Larson, 1971). However, when reviewing various recidivism studies, it is important to keep in mind how recidivism is measured and, more importantly, what is excluded or included in the analysis (e.g., technical violations and traffic offenses).