Average THC Content in Seized Cannabis Samples (1972 - 2008)

When assessing claims about THC levels in marijuana, it is important to have not only the measures of average THC content, but also the number of samples of each type that were used to derive the measurements. Without knowing the number of samples, it is simply not possible to determine if the reported THC levels are truly representative of the levels in what is being consumed by cannabis users. Likewise, comparing across sample types is illustrative only to the extent that the number of samples is known. The importance of this is readily seen in the chart below left with the data for hash oil. In 2004, the potency of hash oil appears to have skyrocketed to an average of over 30 percent THC. But that is the average of only four samples. As usual, when it comes to the war on drugs, what we aren't being told is much more important and useful than what we are being told. Although all of the available data on average THC content is depicted below, only the data for marijuana and (to a lesser extent) sinsemilla are based on a sufficient number of samples to provide meaningful comparisons. The raw data is confounded not only by the overall number of samples tested, but also by how the samples were treated from the time they were seized to the time they were measured. THC readily degrades in the presence of heat and light, so many of the early years of sample data (even those with enough samples to be be useful) are essentially worthless as there were no quality control procedures in place to govern the handling and storage of the samples. Later data has much greater fidelity as there are, in general, both a larger number of samples for a given sample type, and the samples themselves are more likely to have been handled with standardized procedures. Ultimately, what we need to know and still have no data for, are the highest recorded values for each type of cannabis product for each year. Everyone who was smoking cannabis back in the 1970's, and still does so today, will tell you flat out that there was higher quality marijuana available then too. The big difference today is simply that there is wider availability of higher quality product. Stronger cannabis products aren't "more dangerous" -- they're just stronger, which means less product is required to get the same effect. It's quite similar to the range of alcohol products between beer and whiskey. Whiskey may be "10 times stronger" than beer, but the drug in question (alcohol) is still the same thing.

---

Average THC Content in Seized Cannabis Samples (1972 - 2008)
	Hash Oil		Sinsemilla		Hashish		Marijuana		Thai Stick		Ditchweed
Year	Number	Avg THC %	Number	Avg THC %	Number	Avg THC %	Number	Avg THC %	Number	Avg THC %	Number	Avg THC %
1972	--	--	--	--	6	0.60	34	1.23	--	--	--	--
1973	6	22.00	--	--	11	1.00	33	0.83	--	--	--	--
1974	18	15.34	--	--	53	0.86	113	1.34	1	0.54	--	--
1975	29	13.09	--	--	86	2.28	149	1.05	--	--	--	--
1976	18	18.82	--	--	52	3.28	209	1.94	--	--	--	--
1977	17	18.89	15	3.20	44	1.81	235	1.27	1	4.91	--	--
1978	9	21.31	1	6.28	51	2.15	128	1.47	1	0.82	--	--
1979	9	20.91	10	3.66	43	2.32	191	1.58	1	0.13	--	--
1980	8	16.56	26	6.33	37	2.58	120	1.24	1	0.05	6	0.26
1981	5	17.45	31	6.58	13	2.91	209	1.83	--	--	20	0.32
1982	8	19.88	14	7.10	32	2.69	435	3.07	8	4.60	30	0.44
1983	30	21.36	17	7.87	47	5.47	1145	3.30	7	4.17	60	0.45
1984	33	16.75	36	6.67	59	5.75	1030	3.31	3	5.71	50	0.42
1985	25	15.08	52	7.28	41	6.49	1448	2.83	1	6.26	102	0.48
1986	23	16.51	32	8.43	53	2.66	1372	2.37	6	3.73	124	0.31
1987	22	13.36	43	7.93	63	2.62	1551	2.96	3	4.45	86	0.34
1988	16	8.52	98	7.62	43	3.35	1640	3.18	2	3.37	69	0.39
1989	9	11.96	86	6.95	19	7.06	1075	3.04	--	--	104	0.29
1990	12	16.60	61	10.10	38	5.30	1108	3.24	1	0.12	78	0.33
1991	10	13.07	75	10.53	31	5.21	2149	3.09	--	--	246	0.31
1992	22	13.85	76	8.57	61	5.35	3336	3.08	--	--	107	0.31
1993	17	16.52	123	5.77	39	6.60	3033	3.38	--	--	189	0.37
1994	14	11.57	104	7.49	29	4.60	3032	3.50	--	--	136	0.38
1995	13	13.23	164	7.51	19	3.60	4430	3.73	2	4.52	149	0.41
1996	8	12.82	168	9.23	12	2.52	2148	3.87	--	--	115	0.38
1997	10	18.20	111	11.62	31	8.92	2273	4.25	--	--	57	0.49
1998	5	15.78	101	12.33	15	5.87	2075	4.22	--	--	81	0.39
1999	11	16.21	136	13.38	23	4.94	2450	4.18	--	--	59	0.37
2000	7	28.58	113	12.80	27	4.37	2928	4.67	1	3.27	69	0.35
2001	7	19.44	235	9.55	13	8.48	2398	5.02	--	--	59	0.43
2002	5	22.51	528	11.36	16	9.12	1789	5.11	--	--	67	0.40
2003	4	15.54	538	11.59	16	9.23	1893	4.97	--	--	57	0.38
2004	4	31.32	731	11.91	25	18.95	1815	5.38	--	--	53	0.34
2005	6	6.40	932	11.63	47	11.98	1964	5.25	--	--	52	0.37
2006	3	18.74	1032	11.20	32	29.33	1770	5.58	--	--	49	0.30
2007	18	24.85	1327	11.08	70	27.71	1635	6.11	--	--	40	0.39
2008	12	6.54	1068	11.46	50	23.14	1102	5.81	--	--	26	0.43

Sources: University of Mississippi, Marijuana Potency Monitoring Project^*

* The Marijuana Potency Monitoring Project is sponsored by the US National Institute on Drug Abuse. The sources of the numbers quoted here are as follows: ElSohly, M.A., et al "The Potency of Confiscated Marijuana, Hashish, and Hash Oil Over a Ten-Year Period," Journal of Forensic Sciences, Volume 29, No. 2, April 1984, pp. 500-514 ElSohly M.A., et al "Potency Trends of delta-9 THC and Other Cannabinoids in Confiscated Marijuana from 1980-1997, Journal of Forensic Sciences, Volume 45, No. 1, 2000, pp. 24-30 ElSohly M.A. National Center for Natural Products Research, School of Pharmacy, University of Mississippi, Quarterly Report, Potency Monitoring Project, Report #104, Dec 16, 2008 - Mar 15, 2009 Definitions (All from ElSohly, et al) Ditchweed Fiber type cannabis grown wild in the Midwestern region of the USA. Hashish Hashish is composed mainly of the resin of the cannabis plant, mixed with some plant particles and shaped into a variety of forms such as balls, sticks or slabs which are very hard, dark green or brownish colored. Hash Oil Hash oil is a liquid or semi-solid preparation which is basically a concentrated extract of the cannabis plant material. Marijuana Marijuana in the form of loose cannabis plant material with leaves, stems and seeds; includes cigarettes and those samples which cannot be described otherwise. Sinsemilla Marijuana in the form of flowering tops of the female Cannabis plant with no seeds. Thai Stick Cannabis in the form of leafy material tied around a small stem, a classical form produced in Thailand. Note: By far, the greatest amount of annual marijuana eradication operations involves "ditchweed." Nobody smokes ditchweed. Average THC content in UK samples 1975 - 1981 Claims of THC content and marijuana potency from press reporting.