"• In 2013, 5.7 million persons aged 12 or older used marijuana on a daily or almost daily basis in the past 12 months (i.e., on 300 or more days in that period), which was an increase from the 3.1 million daily or almost daily users in 2006 (Figure 2.15). The number of daily or almost daily users of marijuana in 2013 represented 17.4 percent of past year users.
"• In 2013, 8.1 million persons aged 12 or older used marijuana on 20 or more days in the past month, which was an increase from the 5.1 million daily or almost daily past month users in 2005 to 2007 (Figure 2.15). The number of daily or almost daily users in 2013 represented 41.1 percent of past month marijuana users."

Source

Substance Abuse and Mental Health Services Administration, Results from the 2013 National Survey on Drug Use and Health: Summary of National Findings, NSDUH Series H-48, HHS Publication No. (SMA) 14-4863. Rockville, MD: Substance Abuse and Mental Health Services Administration, 2014, p. 30.
http://www.samhsa.gov/data/NS…
http://www.samhsa.gov/data/NS…