Here, the QS model, containing parameters that are directly interpretable as indicators of either specialization or escalation, was applied to data previously tested for specialization; the results revealed significant differences in the pattern and level of specialization when compared to traditional indices. This model provided clear evidence that, while a small group of offenders increased the severity of their offenses across their criminal careers, many offenders decreased the severity of their criminal activity. This was the first statistical test focusing on differences between particular subgroups. The findings showed that black and white offenders exhibited identical patterns of specialization but different patterns of escalation. The model could be applied to groups differing in age, gender, or offense transition. 5 notes and 27 references