IMO you cant really know. You can only take educated guesses. I know it's not easy to differentiate between cold storage or a wallet that somebody has lost access to for instance.
Discussion
Exactly, circulating supply is an estimation or you take the supply available on exchanges & use that.
I err on the side of what's available on exchanges because it's measurable & obv affects price.
This is the best metric to go off actually;
https://nostr.build/i/d01abc6a1e409c0bf05a0409bc47f0c39f7f4fa8b463b91c221beb820fcf864e.webp