Assessing levels of consumption is often left
to the individual. However, these calculations
are not without their problems and can lead to
underestimations. Comparison between what people claim to consume and annual alcohol sales figures, reveals that sales are up to 40% higher than claimed consumption levels (Boniface and Shelton 2013).
It is acknowledged that self-reporting methods may be partly responsible for this gap, and that individuals may not provide accurate figures,either intentionally or unintentionally.