Mr. Tony Foley:

Both are correct. It depends on the length of the time period. From the 1970s there was a large growth in consumption per head. Females, who generally did not consume as much alcohol - the lady would have the glass of sherry - became almost what one might call normal drinkers. That raised the average level per head. It maximised at the turn of the century, in 2001, and since that year it has dropped from about 14 litres per head to just below 12 litres per head.