I always see these THC content percentages and there is one thing I never see...percent of what? Cannabinoids? Plant material? Oils? I have heard a lot of opinions on this but never a real answer. Anyone got the facts? lol.
THC is a percentage of cannabinoids, though that was not always the case. One reason why 'modern strains' appear to be much more potent than strains from the olden days is in the olden days THC was a percentage of cannabinoids, terpenoids, amino acids, plant matter and various other things. In the olden days THC was a percentage of everything found within all trichome heads, glandular and non-glandular. The inner glands and everything in trichome heads was factored in resulting in a lower watered down percentage of THC. Later most things in trichome heads were removed from the equation and THC became a percentage only of cannabinoids, resulting in a sudden large misleading nonexistent increase in THC percentages.
Something else that factors into THC percentages is that there is not a single standardized test for THC. There are two accepted testing procedures today and each can test samples from the very same buds and end up with test results that can differ by 5% or more. Of course for purposes of marketing, and bragging rights, breeders rely on the test procedure that gives the higher percentages.
What that means is there can be no true factual comparison made of THC levels of strains from the olden days and strains of the modern era, and that advertised claims of THC are questionable. Also, even if a single test procedure were used the percentage of THC found in a strain would not mean every person who grew it would end up with pot with the same percentage of THC as the test results. Breeders have multiple samples tested and will advertise the highest percentage found. All that means is that the genetics are capable of giving someone that high of a percentage of THC, but that high of a percentage of THC is not guaranteed. Someone might get beans from some of the plants whose samples tested lower and they might not be as skilled of growers as others resulting in plants that do not produce THC to their full genetic potential.
Advertised THC levels are much like advertised miles per gallon claims. Your mileage may vary.
Additional: I have in the past posted a comparison of test results where a modern strain was tested using both the old test procedure and the modern test procedure that gives the highest THC results. I have since lost the information so I cannot re-post it and I cannot remember the numbers exactly, but using the modern testing method the strain came in at roughly 21% and using the old testing method the same strain using samples from the same buds came in at something like 8%.
That is a substantial difference, but it does point out how different test results were after the old method of testing was abandoned and the newer one used. It also illustrates why someone cannot rely on claimed THC levels from the olden days as proof that pot was much, if any, weaker then, and that in some cases it was more potent.
Low-grade herb of the past averaged around 3% THC, using the old testing procedure, but higher grade would come in as much as 12% or 13%. If a strain came in at 8% under the old testing procedure and 21% using the new testing procedure a strain that came in at 12% or 13% using the old testing procedure, if tested using the new higher THC level testing procedure would result in a THC level higher than any advertised strain today.