There are only about 15 to 20 dog-bite fatalities annually in the United States, but pit bulls have the dubious distinction of leading the pack. In a study by the U.S. Centers for Disease Control of more than 300 dog-bite fatalities from 1979 through 1998, pit bulls or cross-bred pit bulls caused almost a third of 238 fatalities in which a breed was specified.
A site that looks at the connection of dog breeds and dog bites notes that:
The dogs responsible for the bulk of the homicides are pit bulls and Rottweilers:
"Studies indicate that pit bull-type dogs were involved in approximately a third of human DBRF (i.e., dog bite related fatalities) reported during the 12-year period from 1981 through 1992, and Rottweilers were responsible for about half of human DBRF reported during the 4 years from 1993 through 1996....[T]he data indicate that Rottweilers and pit bull-type dogs accounted for 67% of human DBRF in the United States between 1997 and 1998. It is extremely unlikely that they accounted for anywhere near 60% of dogs in the United States during that same period and, thus, there appears to be a breed-specific problem with fatalities." (Sacks JJ, Sinclair L, Gilchrist J, Golab GC, Lockwood R. Breeds of dogs involved in fatal human attacks in the United States between 1979 and 1998. JAVMA 2000;217:836-840.)
Other breeds were also responsible for homicides, but to a much lesser extent. A 1997 study of dog bite fatalities in the years 1979 through 1996 revealed that the following breeds had killed one or more persons: pit bulls, Rottweilers, German shepherds, huskies, Alaskan malamutes, Doberman pinschers, chows, Great Danes, St. Bernards and Akitas. (Dog Bite Related Fatalities," Morbidity and Mortality Weekly Report, May 30, 1997, Vol. 46, No. 21, pp. 463 et. seq.) . . . .
There is an 8 out of 10 chance that a biting dog is male. (Humane Society of the United States.)
It also noted that:
Studies of dog bite injuries have reported that:
*The median age of patients bitten was 15 years, with children, especially boys aged 5 to 9 years, having the highest incidence rate
*The odds that a bite victim will be a child are 3.2 to 1. (CDC.)
*Children seen in emergency departments were more likely than older persons to be bitten on the face, neck, and head. 77% of injuries to children under 10 years old are facial.
*Severe injuries occur almost exclusively in children less than 10 years of age.
*The majority of dog attacks (61%) happen at home or in a familiar place.
*The vast majority of biting dogs (77%) belong to the victim's family or a friend.
*When a child less than 4 years old is the victim, the family dog was the attacker half the time (47%), and the attack almost always happened in the family home (90%).
"Some 95 percent of the attacks on humans come from dogs that have not been spayed or neutered, and 70 percent of the attacks were committed by unneutered males."
One indicator I've seen for the number of pit bulls in Denver (pre-ban) is that:
Since Denver's city council renewed its 1989 ban on the dogs on May 9, at least 260 pit bulls have been put to sleep in the Rocky Mountain metropolis, spurring a network of pit-bull lovers into illegal action. . . . While it is difficult to estimate how many pit bulls live in Denver, the number of impounded pit bulls has been steadily rising over the past few years, from 103 in 1999 to 652 in 2003.
There are about 68 million dogs in the United States, and Denver's share should be about 100,000 dogs, if it is typical of the nation. Acccording to one story: "In Denver, city officials estimated that there were 4,500 pit bulls, despite the 16-year-old ban."
Thus, while there aren't good numbers on how many dogs of each breed are out there (only about a million dogs have a registered breed), or even widespread agreement on what constitutes a breed, it is safe to guess that the vast majority of dogs in Denver are not pit bulls or rotweillers, despite the fact that they cause the majority of fatalities. Apparently, about 5% of dogs in Denver fit that description despite the fact that they account for a much larger share of serious injuries, so the concern that has caused Denver to ban pit bulls, and has caused Aurora to seriously consider regulating them stringently, is real. This breed may be ten times as likely as the average dog to kill (and probably also much more likely to cause serious injuries).
Both sides play fast and loose with the facts in the debate. Pit bull proponents argue that 99.9% of pit bulls don't kill people, which is cold comfort considering that the dogs that mauled, but did not kill a 10 year old boy in Aurora this month count as non-killers by this standard. The vast majority of serious dog bites are not fatal. The "pit bulls" are nice dogs with bad owners theory may have something to it, but you don't have a grossly disporportionate record of serious dog attacks coming from just a couple of breeds that make up a small proportion of the total number of dogs out there for no reason. But, the pit bull opponents may be overbroad in describing the threat, which involves a pretty specific profile that has more components than just a breed alone.
Of course, small dogs, no matter how vicious are unlikely to kill people. For example, while my brother-in-law apparently has no worries about his Jack Russel Terriers in the presence of children, there is no way that I would trust my children around those dogs which are hyperactive, loud, and very pushy. But, they are also small and it is a safe bet that they couldn't pull off actually killing any child that was more than an infant. Chihuahua's are similarly not known for their ability to inflict damage.
Likewise, few dogs of any kind are capable of killing an adult person alone.
And, it also appears that just about any female dog, or male dog neutered before pueberty is going to be far, far less likely to be a serious threat to humans, than an unneutered male dog.
But, suppose that pit bulls aren't inherently aggressive, and that they are the breed of choice for people who train their dogs to be killers. This doesn't necessarily argue against serious regulation of the breed.
Given the attachment people have to their dogs, one could argue for narrower legislation. A ban on unneutered pit bulls or rottweilers in the presence of children under the age of twelve, for example, might be enough to eliminate the vast majority of the excess risk associated with the breed, while minimally regulating dog owners in situations where there are far less of a risk of death or serious injury. A ban on multiple pit bulls or rottweilers (some of the most frightening attacks have involved groups of pit bulls attacking people, including one that killed an adult woman) might also be worthy of consideration. But, it might not be necessary to ban the one neutered family pit bull in a family where the dog is unlikely to encounter children.