Tuesday 4 March 2014

Drinking time

Sally Casswell's team has a new paper out on Kiwis' drinking habits. Here was their press release on it. I provided a bit of comment on it for Science Media Centre, copied below.
“The article provides a really interesting survey of drinking habits among New Zealand drinkers. They find that, among Kiwis reporting having consumed alcohol in the past six months, alcohol was reasonably affordable and easily accessible. Drinkers attend pubs reasonably frequently and drink relatively less at pubs than they do on the rarer occasions that they attend nightclubs; I expect this reflects that nightclubs may be more likely to be part of a special event than a visit to the local pub.”
“The authors find that individuals purchasing alcohol after 2 am at an on-licence premise were more likely to have consumed larger amounts of alcohol than those purchasing alcohol before 2 am. I think, though, that they are too quick to conclude that closing times would usefully address heavy drinking. If those at the bar at 12 am include a greater proportion of light drinkers, and the light drinkers tend to go home earlier, we would expect that those purchasing alcohol after 2 am would consist disproportionately of those who were drinking more heavily earlier in the evening and who decided to stay at the bar rather than go home.”
“The authors note correlations between the price of drinks at a venue and the amount consumed; they then argue that lower prices cause differences in quantity consumed at different venues. I wonder about causality here. If you know you only want to have one or two drinks, you might go to the cocktail bar with very expensive and fancy drinks; if you’re interested in a heavier drinking session, you might make sure to hit the venue that you know is cheaper. We then could pretty easily see a relationship between prices at venues and quantities consumed that were due in large part to individuals’ choosing venues appropriate to their intended evening. Similarly, they find drinkers paying lower prices for off-premise alcohol were more likely to drink larger amounts. An equally plausible interpretation is that individuals wishing to drink a larger amount will be more likely to have price in mind when making their purchase, while somebody only intending on having one or two drinks might go for a pricier craft beer or a nicer bottle of wine.”
“Whether their findings on price are causal, or simply correlations, matter for policy. They argue that measures like tax increases or minimum prices would particularly target heavier drinking because individuals are more likely to report having paid less for their alcohol on occasions of heavy drinking. But if people are instead choosing lower cost products for those days when they intend on consuming a larger amount, because they’re budget conscious, price hikes would then have a more limited effect on consumption. Byrnes et al (2012) found that price increases in Australia reduced consumption among lighter drinkers, but did not have much effect on heavy drinking among heavy drinkers. Instead, heavy drinkers saved up money for the weekend binge by drinking less on days in which they would have consumed a smaller amount of alcohol. Wagenaar’s earlier metastudy on prices and consumption showed that a 10% increase in alcohol prices was associated with a 2.8% reduction in heavier drinkers’ consumption, but a 4.4% decrease in average consumption. And while the studies in Wagenaar’s metastudy did not focus on prices in the lower ranges, Stockwell, Auld et al (2012) found that a 10% increase in the minimum price of alcohol in British Columbia reduced overall consumption by 3.4%, a figure entirely in line with the prior Wagenaar study. We then need to worry about whether price measures are appropriately targeted, or whether the costs imposed on moderate drinkers by price measures are worth it. Heavy drinkers aren’t nearly as sensitive to price measures as are lighter drinkers. We could similarly curb speeding by putting the petrol tax up to $6/litre, but it might not be the best way of addressing the harms of speeding.”
Dr. Eric Crampton is Senior Lecturer in Economics at the University of Canterbury. His research on alcohol issues is supported in part by the Brewers Association of Australia and New Zealand, through a grant administered by the University of Canterbury.
I'd be interested in knowing whether till-data from pubs, nightclubs, and dance venues followed the same time pattern as they're suggesting in the survey.

In Casswell's story, everybody starts drinking hard at 2 a.m.: the survey shows heavier drinking among those staying at the pub after 2 a.m. because people start drinking more heavily after 2 a.m.. In that world, earlier closing times might reduce harms from heavy consumption. We would then expect to see, within a bar tab, increasing spend after 2 a.m.. I think you'd need to look at patterns within a tab to make a clean call on this: if we only saw increased per patron expenditures, that's equally consistent with Casswell's story (nothing good happens after2 a.m.) and mine (those who are left in the bar after 2 a.m. were drinking more heavily before 2 a.m. as well, and the lightweights have gone home).

I think it's rather more likely that folks who'd intended on going hard started going hard earlier in the evening and then failed to go home before 2 a.m. - the time series is just picking up cohort effects. If my story's right, then we predict that lighter-drinking tabs are more likely to be closed earlier in the evening, that there isn't any particular increase in within-tab expenditures after 2 a.m., but that per patron consumption increases after 2 a.m. because the patron composition changes over the course of the evening. In that world, closing at 2 a.m. doesn't do tons of good because the heavy drinkers already did most of their heavy drinking; they just otherwise would have stuck around the bar for longer. And, a blanket 2 a.m. closing time would do a lot of harm to all-night dance venues where patrons might not be all that likely to be doing much heavy drinking, other than water, after 2 a.m. anyway (MDMA *cough*).

It's at least testable.

In unrelated news, I look forward to tonight's beer tasting at the University Staff Club.

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