September 16, 2012

Crime down, police up.

Twenty-two people didn’t get murdered last year. Another 576 didn’t get robbed. Some 5300 fewer people were ripped off by fraudsters. Those who say we’re drowning in a crime wave appear not to know reported crime is the lowest it’s been this century.

 A good data-based lead in to a story about community policing in the Herald today. Because crimes are much more obvious than non-crimes (I didn’t get mugged today, and my house wasn’t broken into!), it’s easy to think that crimes are increasing whether they are or not.

Two cautionary notes: we can directly observe crime rates going up or down, but the idea that we can directly observe why this is happening is a powerful cognitive illusion.  It looks as though community policing is working, but there could be other reasons for crime going down (for example, whatever is responsible in the US).  Secondly, my reaction to “those who say we’re drowning in a crime wave” is something along the lines of “Really? Who?”  All I could find on the Google were headlines that say “crime wave” when they just mean “more than one crime.”

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Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »

Comments

  • avatar

    Try the Sensible Sentencing Trust for those who would have you believe crime is surging ahead. Here is their selective read on the statistics:

    HOMICIDES

    4000% increase in last 50 years
    2 convictions in 1952 – 80 in 2004/2005
    VIOLENT CRIME

    108% Increase in the period 1990-2000
    Another 7% increase in the period 1999-2005

    12 years ago

    • avatar
      Thomas Lumley

      Ok, that is impressive.

      Note especially that 500% of the 4000% increase in homicide convictions happened from 1952 to 1953, and that homicides have been decreasing for twenty years even without standardising for population size.

      12 years ago