Body & HealthMental model
Most cases come from the group with the small risk.
Geoffrey Rose described it in 1981: a measure can do almost nothing for any individual and still do a great deal for a population. Most alcohol-related problems arise not among dependent drinkers but in the much larger moderate-risk group – simply because it contains so many people.
Useful: Treat only the high-risk group and you miss the majority of the cases.
Source: en.wikipedia.org