As of 2015, dog breeds commonly implicated in serious injuries or attacks include German shepherds, pit bull and pit-types, and mixed breeds. However, there is some evidence that small breeds are also highly likely to bite, but the bites may be less severe since the dogs are not large enough to do serious damage to the average adult.
The evidence on which dog breeds are more likely to bite is mixed and highly dependent on the time period, methodology and circumstances. Controlled studies sometimes show that breeds traditionally considered aggressive, such as pit bulls, are not more likely to bite humans than other breeds. Overall bite statistics can be misleading due to the waxing and waning popularity of various breeds. In the early 1990s, rottweilers experienced a significant surge in popularity and also experienced a corresponding surge in recorded bites. Even traditionally friendly breeds, such as labradors, can top bite statistics in areas where they are particularly popular.
Herding breeds, such as border collies, are also highly likely to bite humans. However, these bites are often small and not widely reported. Herding dogs are likely to bite humans in an attempt to control their behavior.
Controlled studies of aggressive behavior often find that toy breeds have a high level of aggression toward humans. Overall, however, breed is a poor indicator of danger. Individual factors, such as training, socialization, individual temperament and treatment have significantly larger impacts on any given dog's likelihood of biting.