Objective: To estimate the average of and sources of variation in the alcohol content of drinks served on premise in 10 Northern Californian counties.
Methods: Focus groups of bartenders were conducted to evaluate potential sources of drink alcohol content variation. In the main study, 80 establishments were visited by a team of research personnel who purchased and measured the volume of particular beer, wine, and spirit drinks. Brand or analysis of a sample of the drink was used to determine the alcohol concentration by volume.
Results: The average wine drink was found to contain 43% more alcohol than a standard drink, with no difference between red and white wine. The average draught beer was 22% greater than the standard. Spirit drinks differed by type with the average shot being equal to one standard drink while mixed drinks were 42% greater. Variation in alcohol content was particularly wide for wine and mixed spirit drinks. No significant differences in mean drink alcohol content were observed by county for beer or spirits but one county was lower than two others for wine.
Conclusions: On premise drinks typically contained more alcohol than the standard drink with the exception of shots and bottled beers. Wine and mixed spirit drinks were the largest with nearly 1.5 times the alcohol of a standard drink on average. Consumers should be made aware of these substantial differences and key sources of variation in drink alcohol content, and research studies should utilize this information in the interpretation of reported numbers of drinks.