The National Survey of Drug Use and Health conducted a survey in 2008 and determined that 20.1 million Americans or 18% of the total population used illegal substances in the month subject of the survey.  Not surprisingly, marijuana/pot was the drug of choice for at least 15.2 million Americans in that month.  In essence, 1 in 15 people in the country used marijuana in the month subject of that survey.

The survey also indicates that the use marijuana/pot has increased by 5/8% from the 2007 series.  That survey indicates that meth use is down by at least half over the last three year period.