DogsBite.org, that tracks this vital data publicly is Animal People.1
32 U.S. dog bite-related fatalities occurred in 2013. Despite being regulated in Military Housing areas and over 700 U.S. cities, pit bulls contributed to 78% (25) of these deaths. Pit bulls make up about 6% of the total U.S. dog population.2
Together, pit bulls (25) and rottweilers (1), the second most lethal dog breed, accounted for 81% of the total recorded deaths in 2013. This same combination accounted for 74% of all fatal attacks during the 9-year period of 2005 to 2013.
The breakdown between these two breeds is substantial over this 9-year period. From 2005 to 2013, pit bulls killed 176 Americans, about one citizen every 18.6 days
nuff said