Average THC Content in Seized Marijuana (1972 - 2004)

When assessing claims about THC content, it is important to have not only the measures of average THC content, but also the number of samples seized. Without knowing the number of samples, it is simply not possible to determine if the measure from one year is actually comparable to that from other years. 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 in the data for hash oil THC content. In 2004, the potency of hash oil appears to have skyrocketed to an average of over 40 percent THC. But that is the average of only two samples. Clearly, we need to know not only what a given claim is, but also upon what the claim is actually based. 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. Clearly, a wide variety of average THC measures have been made over the years, but the raw data is confounded not only by the overall number of samples tested, but also by how the samples were treated. Since THC readily degrades in the presence of heat and light, many of the early years of sample data are essentially worthless as there were no quality control procedures in place. Later data has much greater fidelity since there are, in general, a larger number of samples for a given product type, and the samples themselves were 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 the marijuana today is really no stronger than that from the past. That is because truly excellent cannabis products were indeed available back then. 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. So you need to use less to get the same effect. It's quite similar to the difference between beer and whiskey. Whiskey may be "10 times stronger" but the drug in question (alcohol) is still the same.

Click names in table to see number of samples vs avg THC for each product type

Average THC Content in Seized Cannabis Samples (1972 - 2004)
Year	Hash Oil	Sinsemilla	Hashish	Marijuana	Thai Stick	Ditchweed
1972	--	--	0.60	1.23	--	--
1973	22.00	--	1.00	0.83	--	--
1974	15.34	--	0.86	1.34	0.54	--
1975	13.09	--	2.28	1.05	--	--
1976	18.82	--	3.28	1.94	--	--
1977	18.89	3.20	1.81	1.27	4.91	--
1978	21.31	6.28	2.15	1.47	0.82	--
1979	20.91	3.66	2.32	1.58	0.13	--
1980	16.56	6.33	2.58	1.24	0.05	0.26
1981	17.45	6.58	2.91	1.83	--	0.32
1982	19.88	7.10	2.69	3.07	4.60	0.44
1983	21.36	7.87	5.47	3.30	4.17	0.45
1984	16.75	6.67	5.75	3.31	5.71	0.42
1985	15.08	7.28	6.49	2.83	6.26	0.48
1986	16.51	8.43	2.66	2.37	3.73	0.31
1987	13.36	7.93	2.62	2.96	4.45	0.34
1988	8.52	7.62	3.35	3.18	3.37	0.39
1989	11.96	6.95	7.06	3.04	--	0.29
1990	16.60	10.10	5.30	3.24	0.12	0.33
1991	13.07	10.53	5.21	3.09	--	0.31
1992	13.85	8.57	5.35	3.08	--	0.31
1993	16.52	5.77	6.60	3.38	--	0.37
1994	11.57	7.49	4.60	3.50	--	0.38
1995	13.23	7.51	3.60	3.73	4.52	0.41
1996	12.82	9.23	2.52	3.87	--	0.38
1997	18.20	11.62	8.92	4.25	--	0.49
1998	15.78	12.33	5.87	4.22	--	0.39
1999	16.21	13.38	4.94	4.18	--	0.37
2000	28.58	12.71	4.37	4.67	3.27	0.35
2001	19.44	9.56	8.48	5.03	--	0.43
2002	22.51	11.39	9.12	5.11	--	0.40
2003	15.54	11.63	9.83	4.97	--	0.38
2004	42.51	13.33	11.22	5.81	--	0.34
Overall Average	17.63	8.61	4.60	3.03	3.11	0.37

2004 data includes samples tested through Nov 8, 2004
Source: 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 #87, Aug 9, 2004 - Nov 8, 2004 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.