The 80 / 20 rule 

The statement that 20% of beer drinkers consume 80% of the beer is an example of the 

Pareto Principle, also known as the 80/20 rule. This principle suggests that in many situations, roughly 80% of effects come from 20% of causes. It is often used to describe disproportionate distribution, such as 20% of customers accounting for 80% of sales or 20% of people being responsible for 80% of a particular activity. 

The 80/20 rule: Popularized by Richard Koch in his book The 80/20 Principle, the rule suggests that a small number of inputs or causes are responsible for the majority of outputs or results.

Real-world examples: In addition to beer consumption, the principle is often cited in contexts like 20% of motorists causing 80% of accidents, 20% of clothes being worn 80% of the time, and 20% of customers generating 80% of profits.

Application to alcohol: Alcohol marketers frequently observe this principle, noting that a small percentage of "heavy users" account for a large portion of total sales. For example, research has shown that the top 10% of American drinkers consume a disproportionately large amount of alcohol. 

"disproportionately" doing a lot of work there.