Sentencing and Unwarranted Disparity: An Empirical Assessment of the Long‐term Impact of Sentencing Guidelines in Minnesota*

Using an interrupted time‐series design, this research note analyzes the long‐term effect of Minnesota's sentencing guidelines on reducing unwarranted disparity in sentencing outcomes that fall within their scope of authority. Unwarranted disparity is defined as residual variation not attributable to legally mandated sentencing factors. Findings suggest that although the sentencing guidelines initially reduced disparity for the no prison/prison sentencing decision, inequality began to revert to preguideline levels as time passed. Further analysis revealed that the guidelines had a permanent impact on reducing disparities in decisions on the length of prison sentence. Overall we observed an 18% decline in disparity for the no prison/prison outcome and a 60% reduction in inequality for the judicial decision as to length of prison sentence. Two explanations for the reversionary trend in the no prison/prison series are highlighted.