We compiled a table of marijuana potency, 1975-2003 from the Annual Reports (Nov. 9. 1999 to Nov. 8, 2003) of Mahmoud A. ElSohly, PhD, Director of the National Institute on Drug Abuse (NIDA) Marijuana Project at the National Center for Natural Products Research, School of Pharmacy, University of Mississippi. (We obtained these documents from a 2004 Freedom of Information Act request to NIDA.)
The compilations follow. See NIDA's chart in PDF format (107 KB) .