Crime goes up and down, and we do not understand all the reasons for this. Although Lott makes a commendable effort to control for as many factors as he can, there are still significant changes in the crime rate that are not explained by his model. A way to test to see changes in the crime rate were caused by the carry law or one of the other factors is to look for differential effects--we would not expect the carry law to affect all crime rates equally. For example, since juveniles are not eligible for the concealed weapon permits, we would not expect the law to affect the juvenile homicide rate as much as it effects the adult rate. With one somewhat problematic exception, we do not find differential effects.