True, that was just one layman's brief pondering of an alternate metric, and I hadn't realized the secular technology trend. I was mainly looking for something that can't be debased because then people will die, but that is also has minimal volatility in demand, supply, and speculation, and requires numerous inputs so as to smooth out the effect of local shocks.

Anything that has numerous inputs will likely be something which is complicated to manufacture and therefore will have increasing efficiency as the technology improves. I can't think of a single good that fits your criteria and hasn'thad substantial technological advancements of how it is made in the last 30 years. This sort of approach might work if one had very steady data for some long historical period with not much technological advancement.