The washington post had an article that basically said the 80/20 rule applied to drinkers (20% consmed 80% of alcohol).

http://www.washingtonpost.com/blogs/wonkblog/wp/2014/09/25/t...

Based on this article (3 pints @ 5% is considered high volume consumption for men) then 30% of the drinking age population falls into that category. If you eliminate non drinkers (less than 1 a week) then it's like 3/5th of drinkers.