hmm interesting hadn't heard that before but makes sense. have an example? (aside from small scale like finding weed farms, lol)
It is a general indirect method to measure it because of the fact that energy/GDP, it can be used in the case of busting miners and weed planters of course, but then they often use-
thermal cameras from helicopters and checking for electricity spikes in the grid, but what I describe is a tool economists use to estimate the size of the informal economy as a whole.