The two initial policy decisions that were largely responsible for this complexity were basing guidelines on "relevant conduct" rather than on the offenses of conviction and specifying in detail the number and precise sentencing value of aggravating and mitigating factors. Given this initial bias toward specificity, it was inevitable that the complexity in the guidelines would become worse as Congress pressed for further distinctions and the Sentencing Commission responded to those statutory actions. The complexity of the U.S. Sentencing Guidelines has detrimental effects on both the perceived and actual fairness of the laws. Although statistical analyses show that the most complex guidelines (as indexed by the length of each guideline, the length of application notes for each guidelines, and the number of amendments to each guideline) are also those that are most often used, there is also evidence that at least some of the complexity in the guidelines (the number of specific offense characteristics in each guideline and the number of cross references) is unwarranted. 2 tables, 3 notes, and 53 references