Murdering statistics

Written By: - Date published: 9:36 am, July 12th, 2010 - 16 comments
Categories: crime, making shit up, scoundrels, spin - Tags:

Something that really boiled my blood a few weeks back, but which I haven’t had a chance to write about yet was this post by National Party pollster David Farrar on the topic of a recent lull in homicides in a single police district. It was the worst kind of politics – a person who knows his argument is false taking advantage of the suffering of people and the ignorance of his audience for petty party political points scoring.

Noting that there had been just one homicide in Manukau this past half year compared to 50 (actually, 48) in the previous two years David wrote: “So homicides have gone from one a fortnight to one in six months. Must be a coincidence with the extra police resources, right?”

Almost certainly yes, it is a coincidence.

You can’t attribute the lower number of homicides in those six months to police numbers, just as the three homicides in the past week in Manukau can’t be linked to police numbers.

As David and anyone with a smattering of statistical knowledge understands, when you have very rare events occurring at random intervals you get clumps of events and periods of none – it doesn’t necessarily mean anything, it’s usually just statistical clustering. The fact is that homicides are very, very rare events – about 1 every 5 days in a population of 4.3 million means (assuming everyone has an equal chance of being a victim) that it would take 26,000 years – four times recorded history! – before the odds of you being a homicide victim would pass 50%.

We can’t credit the Government for the fewer homicides in Manukau in the last half year any more we can blame for the tripling of homicides in Tauranga. Or for the three homicides in the past week in Manukau. Throw darts at a dartboard blindfolded and you’ll get clumps of darts and areas with no darts – it’s not a meaningful pattern – it’s coincidence.

Nationwide, homicides totaled 30 over the last six months, a little below the average of 35 for the previous 30 six month periods but, again, not enough to be statistically meaningful. A welcome drop in the number of homicides over a short period in one area proves nothing and anyone with thinks about it knows that. As Rex Widerstrom commented on David’s post “I sometimes wonder how DPF can sell his services as a statistician at the same time he uses his blog [for this statistical gibberish]”.

Where is a evidence for a causative link between the extra police in Manukau and the fewer homicides in those few months? There isn’t any. Just as National’s cuts to police numbers in other areas haven’t unleashed a wave of murders.

Most homicides in New Zealand are the result of family violence. The way to reduce them is the way we can reduce all family violence – with education campaigns and employment. The numbers show a degree of link between the unemployment rate and homicides, and a much stronger link between unemployment and the general crime rate.

If David really cared about reducing crime, rather than dishonest political point scoring on people’s suffering, he would join us in calling for the government to get serious about job creation – that is the single most effective tool the government has to make our communities safer.

16 comments on “Murdering statistics ”

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  1. ianmac 1
    12 July 2010 at 10:19 am

    When reporting the recent murder on TV they said several times that “since the increase in police in South Auckland, the number of murders has dropped from 50 to 2”. So David Farrar has done his job well. Crusher Collins can bask – like a shark?
    I hope that the number stays low but as you say the number of murders per 10,000 is so low that the stats are almost meaningless.

  2. Horse 2
    12 July 2010 at 10:41 am

    The NZ Police regularly do the same kind of thing with road fatalities to either (a) justify their “crackdown” if accidents happened to be lower on a weekend or (b) call for increased resources etc if accidents happened to be higher.

    • Rex Widerstrom 2.1
      12 July 2010 at 9:29 pm

      Which is why – while I’m no fan of Collins – I wonder if it wasn’t the police hierarchy which proudly reported this “success” to their Minister, knowing full well she was enough of a dupe to fall for it (as was just about every journalist who received it).

      The police as master PR tacticians, from whom many could learn. Take something everyone wants, claim credit when an anomaly occurs, then use that to justify getting more of what you want.

      So, teacher unions – the next time some savant kid shows up, sit him alone in a classroom for the year watched by two teachers. Then take his A+ test results and get some shonky “expert” to attribute it all to a teacher / student ratio of 2:1. Bingo! Increased staff numbers 😀

  3. Lindsay 3
    12 July 2010 at 11:12 am

    If a 50 percent reduction in joblessness equates to, at best, a 22 percent fall in crime and job creation is the “single most effective tool the government has to make our communities safer” then the outlook is grim.

    • Bright Red 3.1
      13 July 2010 at 6:06 am

      Lindsay’s search for the silver bullet continues… she throws away bronze bullets by the dozen in the process.

  4. Butyeahbutnahyeahnah 4
    12 July 2010 at 1:19 pm

    Just as long as no one looks at restricting the supply of alcohol or the relationship between alcohol and domestic violence… Can’t have anyone touching my fruit and veg subsisdised, one in moderation, I tell you whats wrong with kids of today, alcohol. No, I’m not addicted I just get really shirty when I don’t have free access at ever dairy in the country to my one a day, habit, (that isn’t at all habit forming).

    If only Labour had the honesty and intent to make safer alternetives legal, isn’t time to look at the bigger picture?

  5. ghostwhowalksnz 5
    12 July 2010 at 1:44 pm

    You dont have to go into the randomness of murder, to blow apart the Farragoblog comments – which came from TV3 to start with.

    They are comparing an actual offence , ‘murder’ with a crime category ‘homicide’
    When you look up the offences included in homicide ( which isnt an actual offence)
    they are
    Murder
    Manslaughter
    Attempted murder
    dangerous driving causing death ( or similar)
    Thats why it was such bullshit, they werent even comparing the murders from one year ( part year) to the next but with a bigger category.
    Of course the whole fabrication was concocted out of Collins office and fed to gullible slugs at TV3

  6. Bored 6
    12 July 2010 at 2:47 pm

    I have not heard of DPFs imminent murder, nor the extremely low likelihood of this event (despite the large number of pleas of extenuating circumstances that might be bought before the court on behalf of whoever might do this foul deed). Maybe a rogue statistician out there might just lose his rag at DPFs outrages against a proud profession, on the other hand they might just do a quick Chi test on his forehead with a biro and conclude that numbers dont stick on their David, and that perhaps he is just a regression error.

  7. kriswgtn 7
    12 July 2010 at 9:11 pm

    http://newzeelend.wordpress.com/killed-in-nz/

    He cant actually beat these stats with any crap

    Scarey and disturbing stats

    Captcha=oh

    • ianmac 7.1
      13 July 2010 at 5:57 pm

      Crikey kriswgtn! Glad I will be a Kiwi when my number comes up. What stats! What credibility!

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