Cannabis Potency by Year

The Cannabis Potency Monitoring Project, product of a grant from the National Institute on Drug Abuse, is based at the University of Mississippi's School of Pharmacy. Each year since 1975, the Project has issued reports concerning the THC levels of seized cannabis samples sent to them by law enforcement officials. The figures in the following table were published in September 2010.

Potency data are based on samples seized by federal, state and local law enforcement and subsequently sent to the University of Mississippi for analysis. The University received more samples in some years than in others. For example, 12 samples of sensimilla were reviewed in 1985; in 2012, that number exceeded 1,500. It wasn't until 2002 that the number of sensimilla samples examined exceeded 100. For this reason, caution should be exercised when comparing potency data before the new millennia to after it.

To account for the inconsistencies in sampling, three-year moving averages were applied to the annual numbers to smooth out out peaks and valleys. This smoothing finds that the percentage change based on the three-year averages, from 2005 to 2008 was +3.9% THC for commercial 'marijuana', -1.3% for 'sensimilla,' and +6.6% for 'kilobricks.' Average changes for loose-leaf, CBD, CBC, and CBN were negligible. The most recent three-year average potency values for these seized samples were 5.8% THC for commercial 'marijuana,' 11.2% THC for 'sinsimilla,' 9.9% THC for 'buds,' 6.5% THC for 'kilobricks,' and 2.1% THC for 'loose-leaf.' The most recent three-year moving potency averages for the cannibinoids were 0.47% for CBC, 0.30% for CBC, and 0.26% for CBN.

Cannabis Potency by Year
Year Marijuana Sinsemilla Flower Buds Kilobricks Loose-Leaf   CBD   CBC   CBN
2008 5.81 11.46 10.14 6.85 1.82 .41 .26 .27
2007 6.11 11.08 9.81 6.73 2.09 .48 .25 .24
2006 5.58 11.20 9.73 6.03 2.30 .53 .25 .28
2005 5.25 11.63 9.81 5.67 2.19 .46 .27 .32
2004 5.38 11.91 9.19 5.41 2.16 .46 .25 .28
2003 4.97 11.59 8.39 5.13 2.18 .46 .24 .23
2002 5.11 11.36 8.03 5.07 2.25 .42 .24 .22
2001 5.02 9.55 8.88 4.99 2.31 .47 .23 .28
2000 4.67 12.80 9.33 4.40 2.31 .45 .21 .34
1999 4.18 13.38 9.97 3.84 2.24 .43 .21 .38
1998 4.22 12.33 8.40 4.66 2.41 .41 .21 .23
1997 4.26 11.62 8.71 4.66 2.79 .40 .25 .20
1996 3.87 9.23 6.94 4.44 2.26 .42 .23 .23
1995 3.73 7.51 6.01 3.84 2.01 .31 .20 .31
1990 3.24 10.10 6.27 3.76 -- .38 .18 .19
1985 2.83 7.28 5.67 3.80 -- .28 .14 .23

Notes: All numbers are percentages. The THC percentages are "Non-normalized Delta-9 THC Concentrations in Different Forms by Year Confiscated 1985 - Present," and cannabinoid percentages (CBD, CBC, CBN) are "Non-Normalized Cannabinoid Averages of Illicit Cannabis Samples by Year Seized." The cannabinoids CBN = Cannabidiol, CBC = Cannabichromene and CBN = Cannabinol.

 
Sources:

Journal of Forensic Sciences, "Potency Trends of D9-THC and Other Cannabinoids in Confiscated Cannabis Preparations from 1993 to 2008," Mehmedic, Zlatko; Chandra, Suman; Slade, Desmond; Denham, Heather; Foster, Susan; Patel, Amit S.; Ross, Samir A.; Khan, Ikhlas A.; ElSohly, Mahmoud A. (September 2010, Vol. 55, No. 5) pp. 1209-1217.
http://home.olemiss.edu/~suman/potancy%20paper%202010.pdf

Quarterly Report #104, Dec. 16, 2008 - March 15, 2009, University of Mississippi Potency Monitoring Project (Oxford, MS: National Center for Natural Products Research, a Division of the Research Institute of Pharmaceutical Sciences, 2008), Mahmoud A. ElSohly, PhD, Director, NIDA Marijuana Project (NIDA Contract #N01DA-5-7746), pp. 8 and 10.
https://www.ncjrs.gov/pdffiles1/ondcp/mpmp_report_104.pdf

Quarterly Report #100, Dec. 16, 2007 - March 15, 2008, University of Mississippi Potency Monitoring Project (Oxford, MS: National Center for Natural Products Research, a Division of the Research Institute of Pharmaceutical Sciences, 2008), Mahmoud A. ElSohly, PhD, Director, NIDA Marijuana Project (NIDA Contract #N01DA-5-7746), pp. 8 and 10. http://www.whitehousedrugpolicy.gov/pdf/FullPotencyReports.pdf

Quarterly Report #76, Nov. 9, 2001-Feb. 8, 2002, University of Mississippi Potency Monitoring Project (Oxford, MS: National Center for the Development of Natural Products, Research Institute of Pharmaceutical Sciences, 2002), Mahmoud A. ElSohly, PhD, Director, NIDA Marijuana Project (NIDA Contract #N01DA-0-7707), Table 3, p. 8.