Daily/Frequent Marijuana Use in the US
"In 2011, an estimated 16.7 percent of past year marijuana users aged 12 or older used marijuana on 300 or more days within the past 12 months. This translates into nearly 5.0 million persons using marijuana on a daily or almost daily basis over a 12-month period.
"• In 2011, an estimated 39.1 percent (7.1 million) of current marijuana users aged 12 or older used marijuana on 20 or more days in the past month. This was similar to the 2010 estimate of 39.8 percent or 6.9 million users."
Substance Abuse and Mental Health Services Administration, Results from the 2011 National Survey on Drug Use and Health: Summary of National Findings, NSDUH Series H-44, HHS Publication No. (SMA) 12-4713. Rockville, MD: Substance Abuse and Mental Health Services Administration, 2012, p. 27.