Blurred picture of alcohol consumption

Dawn Primarolo suggests that we are drinking more than we thought as a result of changes in the way the Office of National Statistics calculates the average alcohol content of wine glasses (Report, December 14). A more accurate way of assessing consumption should be to look at customs alcohol clearances per adult. But they depend on converting the quantities of beer, cider and wine from bottles using assumptions about average alcohol content. (For spirits, duty is charged on the actual quantity of alcohol released for consumption.)

The assumed strengths of beer and cider have changed little over the past six years, while the strength of wine has gradually increased to 11.81% alcohol in 2006-07. But the average strength of the eight top wines advertised on the Tesco website is 13.5%; if this is representative, customs data could also be an underestimate. I am asking the government to explain how customs calculates average strengths of wine, beer and cider, and this may lead to a more accurate picture.
Eric Avebury
House of Lords

So the Office for National Statistics is to change the ways in which it measures alcohol consumption based on consumer surveys. It is well known that drinkers - and especially the heaviest drinkers - underestimate their own alcohol consumption, partly because they may be too embarrassed to admit the truth, but often because they tend to lose count. A survey conducted here in New Zealand a few years ago showed that the amount of alcohol consumed - according to surveys - was about 25% less than the amount actually sold, according to excise duty records. Surveys of this kind are pretty meaningless.
Derek W Smith
Hamilton, New Zealand