Lies, damn lies and statistics

Len Brown writes in the Herald:

The new Auckland Council will have a lot of work to do to help create a safer environment – police statistics show that Auckland City has more reported crime per 100,000 residents than any other police district in the country, and Counties/Manukau the fourth highest rate.

Now I always get interested when anyone starts talking about the overall crime rate for it is almost a meaningless statistic, as it treats all crime as equal. A brutal homicide is the same as jaywalking (well that is not an offence, but imagine the most minor criminal offence there is).

I always pay most attention to the violent crime rate, and sexual crime rate, as they are the one people worry about most in terms of safety.

So Len Brown is right that in terms of overall crime, Auckland Police District has a higher rate that Counties/Manukau. There were 55,898 and 54,409 reported crimes respectively, which is a rate per 10,000 population of 1328 and 1094.

However if we look at violent crimes, the respective rates are 128 for Auckland and 195 for CM – CM is 52% higher.

Much the same for sexual offences – the rates are 7.8 and 9.8 – CM is 26% higher.

The category that makes up most of the overall crime stats is dishonesty, and the primary offence within that category is theft.

So remember whenever anyone talks about the overall crime rate, ask about the violent and sexual crime rate also. Otherwise a 2% fall in thefts may be masking a 50% increase in violent assaults and rapes.