In the most recent National Survey of Drug Use and Health (2012 NSDUH), seven percent of the US population aged 12 and older reported using marijuana at least once in the past month. Out of this total number of users one-third reported using heavily, i.e. on 21 days or more within the past 30 days1. In fact this figure may underestimate true use, since people tend to underreport in surveys about illegal drug use. Although they make up roughly two percent of the total population, or one third of all past-year users (see Figure 1), heavy users consume 80 percent of the grams of marijuana consumed in the US.