Friday, 6 July 2012

Odoriferous statements

Prime Minister John Key said he didn't think minimum pricing would do much to curb heavy harmful drinking. Jennie Connor is quoted in a press release excoriating Key:
Mr Key announced today that he doesn't believe that minimum pricing for alcohol will change the amount people drink.

"This is contrary to the scientific evidence base about alcohol pricing in general and minimum pricing in particular" said Prof Jennie Connor, medical spokeperson for Alcohol Action NZ.

"Mr Key states that what typically happens is people move down 'the quality curve' and still get access to alcohol. Where does this information come from? On the contrary, minimum pricing specifically targets the very cheapest alcohol options and is predicted to reduce average consumption by removing high-alcohol low-cost products from the market."

"A recent Canadian study has shown that a 10% increase in the minimum price of alcohol reduces its consumption by 16% relative to other drinks".

"And these latest data are consistent with the scientific literature which indicates that increasing the price of alcohol has a positive impact on reducing heavy drinking". [emphasis added]
When I saw the release [HT:], something seemed awfully odd about the bolded quote. What's the reference category, fruit juice? What's meant by "relative to other drinks"? So I dug around a bit for the work she's citing.

Connor is almost certainly referring to this Canadian study, which does argue in favour of minimum pricing. But compare their numbers with the bolded quote above.
The estimates indicate that a 10% increase in the minimum price of a given type of [alcoholic] beverage reduced consumption of that type by about 16.1% relative to all other  [alcoholic] beverages, and a simultaneous 10% increase in the minimum prices of all types reduced total consumption by 3.4% (p<0.01 in both cases). The first estimate may overestimate minimum price effects because it incorporates compensatory increases in consumption of all other beverages. The estimate of the effect of across-the-board changes in minimum prices on total consumption will be biased to the extent that the extra structure we imposed on the model is unrealistic.
Connor is citing the results from the own-price study as being the estimate of the effect of the across the board increase.

Doug Sellman, in the same press release, says
"The PM's statements reek of alcohol industry influence."
As for the bouquet emanating from the Connor/Sellman press release...


  1. Prof Stockwell also testified in Scotland:
    The presentation includes the same 16.1% 'any drink versus the rest' elasticity. But, as you note, the point of minimum pricing is to affect all drinks simultaneously.

  2. Lies.. damn lies and statistics.... this from the very next paragraph in the abstract from the paper lined above...

    "Time series estimates indicate that a 10% increase in minimum prices reduced consumption of
    spirits and liqueurs by 6.8% (P=0.004), wine by 8.9% (P=0.033), alcoholic sodas and ciders by
    13.9% (P=0.067), beer by 1.5% (P=0.043) and all alcoholic drinks by 3.4 % (P=0.007). "
    So a 10% increase in the price of beer will reduce consumption by 1.5%? Not exactly the 16% stated above... and I don't really like the p values for wine, beer or alcoholic sodas... and a 3.4% reducing in consumption overall - can't see how the claims of -1.6 price elasticity can stack up...

  3. Table 4 uses longitudinal data; Table 5 uses time series. Connor cites the biggest numbers possible out of that paper. I've emailed one of the paper's authors asking about why results from Table 4 and 5 are somewhat disjoint; will report back.