Stander and colleagues, in 1989, noted that change in specialization may be caused by two distinct but potentially complementary processes: (a) a change in group composition, where change in specialization is the product of the attrition of offenders who vary systematically in their tendency to specialize; and (b) a change in the tendency to specialize among persistent offenders. Results of the current study support earlier work finding change in the tendency to specialize among persistent offenders. Results also show that those who desist do differ in their tendency to specialize in drug and miscellaneous offenses, thereby suggesting that attrition will influence trends in specialization for these offense types. Post hoc analyses indicate that the relative influence of changes in group composition on trends in specialization is minor. (Published Abstract)