Here's one of the places in Colorado I backpack:
http://www.wilderness.net/NWPS/wildView?WID=485&tab=Area Management Trails are always loaded with unleashed dogs.
I Googled "us dog bite". This was the first link:
http://www.dogsbite.org/dog-bite-statistics.php
Dog bite statistics ::
Each day, about 1,000 U.S. citizens require emergency care treatment for dog bite injury.1 The following studies examine injury occurrence and the dog breeds most likely to bite.
Dog Attack Deaths and Maimings, U.S. & Canada,
September 1982 to December 31, 2012
By compiling U.S. and Canadian press accounts between 1982 and 2012, Merritt Clifton, editor of Animal People, shows the breeds most responsible for serious injury and death.
The combination of large molosser breeds, including pit bulls, rottweilers, presa canarios, cane corsos, mastiffs, dogo argentinos, fila brasieros, and their mixes:
79% of attacks that induce bodily harm
72% of attacks to children
85% of attack to adults
69% of attacks that result in
fatalities
77% that result in
maiming
EDIT: Why in the world do we spend so much time worrying about bear attacks? Based on the actual data, manufacturers ought to be making "dog spray" and specialty "dog guns". I totally want a big huge anti dog gun to carry on the trail. Nationally advertized and instantly recognizable:
FIDO NUKER 2000