Garbage In, Garbage Out?

Maltz and Targonski [34] have examined the county level UCR statistics used by Lott and found it to have extensive gaps--in many states large numbers of counties have 30% or more of their population missing coverage. They conclude that

in their current condition, county level UCR crime statistics cannot be used for evaluating the effects of changes in policy.

I should note, however, that state level analyses do not have the same problem and these give somewhat similar results to the county level one.