Measuring Interjudge Sentencing Disparity: Before and After the Federal Sentencing Guidelines

Abstract

This paper evaluates the impact of the Federal Sentencing Guidelines on interjudge sentencing disparity, which is defined as the differences in average nominal prison sentence lengths for comparable caseloads assigned to different judges. This disparity is measured as the dispersion of a random effect in a zero‐inflated negative binomial model. The results show that the expected difference between two typical judges in the average sentence length was about 17 percent (or 4.9 months) in 1986–87 prior to the Guidelines and fell to about 11 percent (or 3.9 months) in 1988–93 during the early years of the Guidelines. We have not sought to measure the effect of parole in the pre‐Guidelines period, other sources of disparity such as prosecutorial discretion, or the proportionality of punishment under the Guidelines as compared with the pre‐Guidelines era.