Tuesday, 24 January 2012

Dog days of summer... this time with data

Two nice bits of data came of the last round of dog panic.

Here's ACC:
There were 3,435 dog attacks reported to 72 New Zealand councils in 2001/2. From 1989 to 2001, there were 3119 hospitalizations and one fatality due to dog bites. In the year ending 2003, ACC received 8,677 claims for dog bites requiring medical attention. [1]
A recent New Zealand study of adults who made claims to ACC for dog bites found that 26 per cent of the bites occurred in a public place and 21 per cent occurred at home, with the remainder divided between other types of private property. [2] In this study, only 11.6 per cent of dogs were loose and unsupervised in a public place, although other studies have found higher levels than this. Territory defence was the most common reason for a dog to bite, followed by accidental bites due to pain or fear. Pure-bred dogs were responsible for 40 per cent of bites, mixed breeds for 27 per cent and the remainder unknown. The top fi ve pure-bred categories were German Shepherds (8%), Pit Bull Terriers (7%), Rottweillers (6%), Jack Russell Terriers (4%) and Labrador Retrievers (3%).
Here's the underlying survey data, though note that this is just on adult survey respondents; folks seem most outraged about attacks on kids.

As pit bull terriers are pretty uncommon and labs are very common, the conditional risk presented by pit bulls is pretty high, although that could easily be due to that scary people who like to abuse dogs and to intimidate people choose that breed; if that breed were banned, scary people would likely converge on another breed pretty quickly. Note also that a reasonable proportion of mixed breed attacks will likely involve Staffie-crosses.

If less than 12% of dog attacks involved dogs running loose, where ownership would be most difficult to pin down under a liability regime, that increases the likely feasibility of a strict liability plus insurance regime over alternatives.

More data: the Department of Internal Affairs's Dog Safety and Control Report:
Looking at dogs by breed and considering only those with more than 500 in the NDD, the highest rate of dangerous dog classifications are for the pure-bred American Pitbull Terrier with 1.9% of 3,469 classified as dangerous. Next are the cross-bred American Pitbull Terrier (1.4% of 3,258) and the Dogue de Bordeaux (1.2% of 599 dogs). All the remaining 126 breeds with 500 or more dogs in the NDD have a dangerous rate less than 1%.

In terms of actual numbers, the American Pit Bull Terrier pure-bred has the largest number (67) of dangerous dogs in the NDD, followed by the Staffordshire Bull Terrier (48), the American Pit Bull Terrier cross (46), the Labrador Retriever (43) and the German Shepherd (42). Some 352 breeds did not have any dogs classified as dangerous.
This all makes me more confident in my current heuristic: upweight the chances that a dog and its owner are dangerous if the dog is a Pit Bull. That gives no argument for banning Pit Bulls, as scary owners would shift into other dogs - a determined psycho could turn a German Shepherd into a scary attack dog fairly easily.

And in response to a couple of comments on a prior post: the point of a strict liability regime isn't to ensure compensation to those bitten. It's to ensure that an actuarily fair premium is assessed on owners who are compelled to buy liability insurance as part of dog ownership so that owners who pose too great a risk are priced out of the market. But as liability insurance isn't even mandatory for car ownership, I'm less than optimistic about the chances for it in dog ownership.

HT on all of this: Wayne Heerdegen, who spent a bit of time at Treasury working on dog policy.


  1. The underlying survey data makes for interesting reading. My main concern with it is the successful identification of pitbulls. They have been fairly widely demonised in the mainstream media of late, and I suspect there is a fair bit of misidentification going on, as a number of pure and mixed breed dogs look pretty similar. I ran across this interesting site the other day when I was reading about dog attack incidents, it is a pit bull identification tool, to test you to see how long it takes to spot a pitbull among a series of similar looking dogs. Try it and see how you go:
    There is also an interesting publication called the Pitbull Placebo which I haven't read in full, but which purports to dispel some of the myths around the dangers of pitbulls: www.pitbullproject.ca/placebo.pdf

    Note that I'm not an apologist for pitbulls in particular, but the blame is being unfairly placed on the breed in my opinion, whereas should more correctly be aimed at scumbag owners who turn potentially very nice dogs into angry attack mongrels.

    1. Lats, just becuase people may think a dog they see has some pitbull in it even when it doesn't, doesn't mean that when there is a nasty attack media attribution of being a pitbull is wrong. And even if some attacks are wrongly attributed to pitbulls or staffordshire terriers, it doesn't change the following:
      1. Those breeds were specifically created for dog fighting, and are genetically programmed to lock their jaws on a bite and not let go.
      2. It may be true (as breeders claim) that pure-bred pit-bulls are only programmed to attack other dogs, not humans, but pitbulls and staffordshire terriers are deliberately crossed with other breeds, which makes their behaviour unpredictable (but likely with the same jaw-locking instinct)
      3. There is no good reason for anyone to want to own a pitbull; there are plenty of breeds out there that are less dangerous to suit any non-anti-social preference. So yes, rednecks will switch to some other breed, but that is no reason not to ban pitbulls.

      By way of example, in the recent Ashburton tragedy, the dog in question was a pitbull crosses with a doberman. The local council said they had no reason to expect a problem with the dog. Well yes they did: It was a pitbull crossed with a doberman--a dangerous jaw-locking breed crossed with an agressive, completely un-predictable breed. That's like saying there is no reason to expect a problem with a loaded gun in the hands of a child.

    2. I have no clue whether anybody's reason for doing anything is good, whether it's buying a scary looking dog or whatever. "There is no good reason to" precedes all kinds of arguments for banning things I could well have good reason to want.

      What I like about my insurance and liability plan is that nobody has to care about good reasons, just actuarial risk. And while stupid moral panics always screw up assessment of good reasons, profit motives keep actuarial assessments based in reality.

    3. just becuase people may think a dog they see has some pitbull in it even when it doesn't, doesn't mean that when there is a nasty attack media attribution of being a pitbull is wrong.

      Really? If a dog has no pitbull in it, it is still ok for the media to paint it as a pitbull attack? How is that acceptable?

      There is no good reason for anyone to want to own a pitbull

      You mean aside from the reason Eric cited, i.e. certain types of people wanting to own a menacing or tough looking dog? In some circumstances I can see the value of owning a dog which is intimidating - property protection being at the top of the list. The dog doesn't need to be a vicious killer, but giving people pause before they enter your property - I can see how some folk would value that.

    4. Lats, I did not mean to say that it is O.K. for a non-pitball attack to be labelled as one. I meant that evidence that people can't spot a pitbull by looking at photos doesn't mean that when attacks are reported in the media the same Bayesian probabilities apply. Typically, the media go the local council who have records of the dog's type at registration.

      And. there are plenty of dog breeds that can perform an adequate protection role, without being a breed that locks its jaw on a bite and is inclined to attack people the size of dogs (i.e. children).

    5. Seamus: Do you really hold the "Can see no good reason to own X" position, or was that just late night shorthand for "I can't believe that the utility differential for owners of those dogs relative to other comparable but less risky dogs outweighs the costs they impose on bite victims." I'm really hoping the latter.

    6. Eric: The word "good" in the sentence, "There is no good reason for anyone to own a pitbull", does include a few positive and normative statements. It is shorthand for, "there is no utility function that would be consistent with my sense of morality under which someone maximising utility with full information would choose to own a pitbull".

    7. Either you have a lot more information about dog behaviour and genetics than I do, or you're a lot more confident to make those kinds of assessments than I am.

      Is that statement the basis for your call for a ban on the breed?

  2. I think we have had ample examples of media laziness on economic issues cited here by the authors of this blog to question the validity of dog breeds as reported by the media. Oh and the jaw locking thing is a bit of a myth. There is nothing peculiar about the anatomy of any particular breed of dog which means it locks in place upon biting. I refer you to the following from the Pitbull Placebo link I cited above:

    Dr. Howard Evans (Professor Emeritus, College of Veterinary Medicine at Cornell University, Ithaca New York and author of the world’s definitive work on canine anatomy [Anatomy of the Dog]), in conjunction with Dr. Sandy deLahunta, one of the foremost dog
    neurologist in the country, along with Dr. Katherine Houpt, a leading dog behaviorist wrote the following statement about the “locking jaw” in Pit bulls:
    “We all agree that the power of the bite is proportional to the size of the jaws and the jaw muscles. There is no anatomical structure that could be a locking mechanism in any dog.”

    Research on the functional morphology of the jaws of various dog breeds conducted by Dr. I. Lehr Brisbin of the University of Georgia showed that:
    “there were no mechanical or morphological differences between the jaws of American Pit Bull Terriers and those of any of the other comparable breeds of dogs which we studied. In addition, we found that the American Pit Bull Terriers did not have any unique mechanism that would allow these dogs to lock their jaws.”

    Some dogs certainly are more tenacious, and like you and Eric I would certainly give dodgy looking characters with mean looking dogs a wide berth, but I really think there is a lot of misplaced paranoia about certain breeds of dogs.

    As I said in my first post, I'm not an apologist for pitbulls or any other breed (apart from Golden Retrievers of course, because I have one) but I do think we too quickly look to blame the dog when it is the mistreatment at the hands of the owner that has turned it nasty.

    1. Lats: I am no expert and so was just going with what I have read in the media (which, as you point out, is probably dangerous), but I had never thought that the notion of "locking" an anatomical one. I thought it was one of personality: dogs created by selective breeding to be good pit fighters are, by nature, tenacious biters.

      I think there are very good reasons to give members the tatooed fraternity (Billy Connolly's term for pitbull owners) a wide berth, but more reason to give them a wide berth when accompanied by pitbulls than when accompanied by golden retrievers, even once you control for the Bayesian updating of owner type that dog breed implies. That is, I reckon I could protect my children from an attack from a nastily raised retriever. I don't believe that about a nastily raised pitbull.

    2. Thanks for the clarification Seamus, I more fully understand now, and I am not entirely unsympathetic of your view on dangerous dogs. However, I'm no great fan of the response by middle-class do-gooders to ban things they don't like, so I'm naturally opposed to calls to regulate available dog breeds out of principle. Note that I do not include you in the above category.

      The sad thing is that people out there do think it appropriate to treat their dogs poorly and train them to be more aggressive than usual. This sometimes ends in people being hurt and dogs being euthanised. It is a pity, because it is quite possible to raise a dog that doesn't bite people needlessly, but which will still bark its head off to warn you of strangers. Don't get me wrong, I have no problem with dogs which have bitten people being put down, sometimes this is the safest option, but in these cases the dog and victim suffer because of the actions of the owner.

      I don't know what the answer is. My gut reaction is for some sort of regulatory regime surrounding dog ownership, but that smacks a little of paternalism. Maybe Eric's insurance scheme has merit, a way of pricing undesirables out of the dog ownership market. My concern is who gets to decide who is a good dog owner, and what criteria do you use to determine this, especially for someone who has no prior history of dog ownership?

  3. ACC, through its socialisation of irresponsibility, seems to me to have contributed to this situation. Public funding of health, without recourse according to circumstances, has also done its bit.
    Jeff W

    1. I wouldn't disagree, but neither would I want to trade the current system for American tort law and property owners being terrified to let anybody do anything.

    2. No, agree about the US system, but our system has its downfalls as we increasingly build a society in which personal responsibility is absent, and a social welfare system that we can't pay for. Can a middle way, encouraging personal responsibility but providing a basic safety need be found? And if it can be found, do we first have to go bankrupt so that the media and then people of NZ accept it?
      A long way from dogs, but the damage caused by some dog owners is an indication of the problems we face.
      Jeff W