I think the big problem with calculating fatal bites is due to the fact that some "pit-like" dogs are miss-categorized.
also, please see below.
http://www.arottalove.org/docs/bf_bite_stats.pdf
Pit mixes are usually lumped into the pit stat and all other not pit mixes are in their own stat.
On average 9 children a year die from pitbull attacks and 3 die everyday from their parents.