There's something special about weed which was grown under the sun, rather than indoors. The "high effect" may be better. This implies that the measured percentage of THC may not be related to the "high effect" to any massive extent.
A medical marihuana dispensary I rarely visit in my town is selling "sun-grown" weed. I tried it and I was very surprised at the overall effect. I felt noticably more "high" than I usually do from using weed. But outdoor grown weed will usually exhibit lower THC than indoor grown.
This "sun-grown" local legal medical marihuana appeared to be normal "kind-bud", like any other indoor grown. It had that same appearance, chunky bud frosted white with visible THC crystals. But it was not grown indoors, but rather in an outdoor, but very protected outdoor, environment apparently. The price was US$60 for 1/2 ounce, which is an enormous amount of weed for the price.
I visited some more local pot shops (dispensaries) and found some more outdoor grown weed. Turns out, some suppliers were growing already in greenhouses, suppliers I had never encountered before as each dispensary may be required to produce or acquire most of its own supply. (Not sure.)
Why does outdoor grown weed have a greater "high" effect than indoor grown? Why is science always lagging behind empirical testing? And what produces the "high effect" if not THC?
Could it be that weed grown under high-UV light exhibits a greater "high" effect? Or does the sun exert a special effect on marihuana plants?
In Europe, they generally use "mercury vapor" grow-lamps which produce more ultra-violet light. Some have also stated that weed grown at high altitude (in high UV sunlight) produces a better "high" effect.