answer:One thought is that, aside from “wolf-dog hybrid”, “Pit Bull” is the only dog on this list that isn’t an officially recognized breed. In reporting bites and attacks, any mixed-breed dog that is muscular and has a block head gets called a “Pit Bull”. Right there, you’ve described a large proportion of the dogs running loose in American cities. When you do this, you end up comparing dogs that people have typically paid quite a lot of money for (and, presumably, get treated as valued animals) with dogs that have no status-symbol or monetary value and are treated accordingly. Dogs take their social cues from their owners (if they even have owners). These stats say more about the kinds of treatment these different sorts of dogs tend to receive than about the dogs themselves.