The following classification for the types of sentence imposed comes from Variable Codebook for Individual Offenders – Standardized Research Data Files for Fiscal Years 1999-2007. These descriptions are those used by the U.S. Sentencing Commission and come from the 2007 Sourcebook of Federal Sentencing Statistics, Appendix A.
The Fine Only category includes those offenders that received neither a prison or probation sentence, but only a fine.
The Prison category includes offenders sentenced to a term of imprisonment only, with no additional conditions of community confinement, home detention or intermittent confinement.
The Prison plus confinement conditions category includes all cases in which offenders received prison and conditions of alternative confinement as defined in USSG §5C1.1. This category includes, but is not limited to, Zone A, Zone B, or Zone C cases receiving prison with additional conditions of a term of community confinement, home detention, or intermittent confinement.
The Probation Only category includes the number of offenders who received a term of probation without a condition of community confinement, intermittent confinement, or home detention.
The Probation plus confinement conditions category includes the number of offenders who received a term of probation with a condition of community confinement, intermittent confinement, or home detention.
Prison sentences for any offender are expressed in months. Currently the U.S.S.C. assigns life sentences a value of 470 months. Prior to FY 1993, the U.S.S.C. assigned life sentences 360 months. Those who received only probation or probation plus confinement conditions were not included in mean prison sentence calculations.