Burnaby's numbers for pit bull bites are questionable

Dear Editor:

The City of Burnaby is considering new breed-specific legislation for pit bulls. However, the mayor and city council seem ready to make important decisions concerning their safety based on very faulty research and misinformation.

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I am an associate professor of applied mathematics at Simon Fraser University; I have also been a resident of Burnaby since 2007. For what it's worth, I am not a pit bull owner.

The director of finance has produced a report for council, though the data in this report is of dubious quality, and does not support the conclusions the report draws, namely that dog bites are on the rise and these bites are being made disproportionately by pit bulls. The report takes two data points (dog bites in 2007 and 2012) and argues that there is an increase in dog bites of 17.4 per cent. This analysis is superficial and misleading. More critically, the report does not consider whether the change in the number of bites is simply a result of a change in the dog population in Burnaby.

The report presents bite data for pit bulls and German shepherds, but it does not indicate whether the breeds are being identified visually or by DNA analysis. Identifying breeds by sight is notoriously error prone. This comparison also greatly exaggerates the disproportionality of pit bull bites by lumping "pit bull,” a term used to represent a number of breeds, against a single-breed of dog (German shepherd). The report states, "The number of bite incidents involving pit bulls in Burnaby is amplified by the fact that this type of dog accounts for two per cent (113) of licensed dogs in the city", while German Shepherds account for 5.4 per cent of licensed dogs. The report ignores the fact that owners self-report the breed of their dog when getting a licence, which might, for obvious reasons, lead to an underestimate of the number of pit bulls. Another issue notably absent from the report is the issue of causality: are these bites occurring because pit bulls or German shepherds are inherently aggressive, or are they a consequence of irresponsible or negligent ownership, or is there some other mechanism?

The report also includes data from a highly biased source, dogsbite.org, to argue that pit bull bites are especially deadly. This website is run by a dog-bite victim with no apparent scientific advisory board. They do not seem to have considered data and analysis available from more neutral and credible organizations, nor from peer-reviewed, scientific publications. For example, they have ignored a scientifically conducted study that appears in a special report from the Center for Disease Control and Prevention of the U.S. government. This special report concludes, "Although fatal attacks on humans appear to be a breed-specific problem (pit bull-type dogs and Rottweilers), other breeds may bite and cause fatalities at higher rates."

I believe that if city council is basing important, public policy decisions concerning the safety of its citizens on any data, it is obligated to ensure that the data is being collected and analyzed using sound scientific principles. I encourage the mayor, city council and staff to engage the Statistics Department at SFU, whose statistical consulting service provides expert statistical advice to individuals involved in data-based research projects.

No matter how Burnaby residents feel individually about pit bulls and breed-specific legislation, they should be aware that the mayor and council will be basing their decision on a questionable report prepared by Burnaby city staff. This report contains faulty research and misinformation; quite simply, it doesn't make the grade.

Dr. Mary-Catherine Kropinski
Associate Professor, Department of Mathematics
Simon Fraser University

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