The Demon Drink

On 3 News last night, we got a tour of South Auckland, just missing various drunken disturbances.   The video starts “3News has uncovered some shocking figures about the amount of alcohol some offenders are drinking” , and the webpage story says  “new research has revealed the alarming impact alcohol is having on crime“.

That’s approximately truish.  The `new research’ is a report dated December 2010 by the New Zealand Drug Use Monitoring (NZ‐ADUM) research programme at Massey University.  They surveyed 800 arrestees in Whangarei, Auckland Central, Wellington Central, and Christchurch Central, asking them about their drug and alchol use.   And there was a lot of drug and alcohol use — evidently, police arrests are selecting for people who are insufficiently risk-averse in all sorts of ways.  The figures possibly qualify as ‘shocking’, with arrestees reporting an average of 12 standard drinks both on typical days when they drink, and on the day they were arrested.  Some people reported much higher consumption, and some reported none.

3News compares this to “The average New Zealander drinks around two standard drinks a day”, which looks like this StatsNZ figure on total alcohol sales.  In addition to the problems of comparing self-reported drinking with sales data, the national average is over all days and the arrestee average is over days when they drank.  Since the arrestees reported drinking an average of about 1 day in 3, the correct comparison to 2 drinks/day is 12/3=4 drinks per day, about twice the NZ average.    The arrestees also consumed more tobacco, more cannabis, more P, more opioids, more ecstasy, and more of everything else than the average Kiwi; in fact, as far as I can tell alcohol showed a smaller difference than any of the other drugs — mostly because the average for all New Zealanders is fairly high.

The other notable statistic about drinking is that the average drinks per day that they drank was the same as the average drinks on the day they were arrested.  That is, although many of the arrestees were drunk when they were arrested, they were no drunker than they usually are on about one day in three.   The relative risk of arrest given their heavy drinking for these arrestees is thus about 3, which is a lot smaller than I would expect even without the headlines.  If you read the report, while alcohol is unquestionably a problem, it is far from the only problem that the arrestees have.