I was thinking the same thing. It should be something like dog bites per 1,000,000 residents or something like that. Then, the rankings would probably change.
Per resident or per number of dogs? City populations are going to have fewer dogs and the dogs in cities are going to be leashed or in doors and less likely to bite.
This doesn't really matter from the point view of the victims of the bite. It should be normalised by number of man-hours worked.