Investigation of the effect of a multi-buy discount ban on off-trade alcohol sales: a natural experiment in Scotland

Abstract

BackgroundThe Alcohol etc (Scotland) Act 2010 was implemented in Scotland on Oct 1, 2011, and included a ban on multi-buy discounts of alcohol in Scotland's supermarkets and off licences (ie, off trade). The main aim of the legislation was to remove the price incentive for consumers to purchase more alcohol than they may otherwise have intended and, in turn, to reduce population levels of alcohol consumption. Alcohol sales data provide the best estimate of population alcohol consumption. We have investigated the effect of the introduction of the Alcohol Act on off-trade alcohol sales in Scotland. MethodsWe obtained data for the volume of pure alcohol sold off trade in Scotland and in England and Wales from market research specialists Nielsen (Oxford, UK) for individual weeks between January, 2009, and September, 2012 (appendix). Sales estimates were produced from electronic sales records from most large multiple retailers and a weighted stratified random sample of smaller retailers. We have previously shown that alcohol retail sales data offer a robust source of data for measurement and monitoring of alcohol consumption in Scotland and England and Wales. We used interrupted autoregressive integrated moving average time-series models to test for any change in off-trade alcohol sales (all alcohol and by drink type) after the introduction of the Alcohol Act in Scotland. Models accounted for underlying seasonal and secular trends and were adjusted for changes in other potential confounding factors including disposable income, alcohol prices, and on-trade alcohol sales. Data for these covariates were obtained from the Scottish Government and Office for National Statistics; Nielsen and Office for National Statistics; and CGA Strategy (Stockport, UK), respectively. To provide a concurrent control group, we did the same analyses using data for England and Wales, where the Alcohol Act does not apply. FindingsThe introduction of the Alcohol Act was associated with a 2·6% decrease in per-adult off-trade alcohol sales in Scotland (95% CI −5·3 to 0·2). This decline was driven by changes in off-trade wine sales, which decreased by 4·0% after the Act was introduced (95% CI −5·4 to −2·6). The Act was also associated with reduced sales of pre-mixed alcohol beverages (–8·5%, 95% CI −12·7 to −4·1), although these account for a very small proportion of total off-trade sales (1%). The Act was not associated with changes in sales of spirits, beer, or cider or perry in Scotland. There was no evidence to support an association between off-trade alcohol sales and the dummy Alcohol Act variable in England and Wales. InterpretationThe introduction of the Alcohol Act was associated with reduced off-trade alcohol sales in Scotland, largely attributable to a decline in wine sales. Key strengths of our study include the use of objective data for alcohol sales rather than subjective data on self-reported consumption, and the adjustment of our time-series models for underlying trends and potential confounders. Limitations include the exclusion of alcohol sales by certain retailers, the inability to disaggregate population sales estimates by different subgroups, and the short period after implementation of the Act. However, similar changes were not noted in England and Wales, where the Act does not apply, which lends weight to the hypothesis that the changes witnessed in Scotland were as a result of the Act rather than other unmeasured factors or biases. Thus, legislation to ban alcohol discounting seems an important policy in the mix to reduce population alcohol consumption levels. FundingPurchase of the sales data was funded by the Scottish Government as part of the wider Monitoring and Evaluating Scotland's Alcohol Strategy portfolio of studies.