Yes thank you for your reaction to my stab at giving a figure for this very difficult to quantify statistic. Your point is well taken that using wallet addresses may significantly overestimate BTC owners/users, as longer term users may have ten or more of those 21.5 million wallet addresses with 0.001 BTC - which as you say is dust only worth ~$7 at the current BTC price. I note replies above though, querying if I’ve underestimated because of people exchanging altcoins on exchanges for some BTC which they them keep in the exchange wallet without a private key - and I’m sure there are many people like that, and if we added up the active users on say the biggest 25 exchanges including the 15 million users on Coinbase we may well come up with a figure of 40 million people at least half of whom prolly own some BTC.

A real issue also alluded to in the good comments above on my post is how do we define a bitcoin ‘owner’ or ‘user’ - do we call someone got 0.001 BTC from playing a faucet and who now has it sitting in a wallet with no idea what to do with it an owner or user? - probably the former, but not the latter like we would with someone who understands blockchain technology and private wallets and keys and who has bought and traded bitcoin and who shows interest in forums like this (that I believe has 1.5 Mil members?) or Reddit bitcoin and crypto channels (which have about 1 Mil users I’d say) to further their knowledge of bitcoin and crypto.

And like you my gut reaction was that bitcoin ownership and use was rare, but I think it’s human nature with rare things to underestimate the incidence. It reminds me a bit of the same problem knowing the real incidence of an uncommon medical condition I suffer called narcolepsy, which is ironic as I’m a retired senior sleep physician. Diagnosing and treating narcolepsy requires the sleep doctor to be interested in it and looking for it and to send the patient for specialised daytime sleep testing that is usually not available in most sleep labs they run - so it’s felt that a lot of people with this debilitating and treatable condition go undiagnosed. The incidence in the population is usually given in the literature as 0.05 to 0.1%, but as Wikipedia notes - https://en.m.wikipedia.org/wiki/Narcolepsy - some studies show an incidence up to 0.5% - which is that same figure I came up with for BTC ownership. I’m sure the 0.1% figure that’s usually bandied around is too low from my own experience as a sleep doctor where I naturally had an interest in narcolepsy and looked for it in my patients especially young very sleepy ones who were unlikely to have the far more common sleep apnoea we mostly diagnosed and treated and my sleep labs could test for it and I had about 150 patients on effective treatment for it after ten years - whereas other highly regarded sleep physicians who were friends of mine had no patients diagnosed for it as they didn’t seem interested in looking for what was a fairly new condition and they couldn’t test for it. I would definitely say that 0.5% incidence figure is correct, rather than 0.1% figure because a lot of patients are unfortunately never diagnosed.

So the point I’m making I suppose is that perhaps 0.1% ownership of bitcoin by adults in the world is a more conservative estimate, if we assume each owner has an average of 5 wallets with 0.001 BTC or more - which would be 4.3 million people, and that would tie in with the say at least 3 million people I’d estimate are active on crypto forums and sites like this and Reddit and Facebook and telegram and twitter and medium and steemit and discord. But just looking at ownership of $7 of bitcoin or more active or inactive, I wouldn’t be surprised if BTC ownership is up to that figure of  0.5% of the adult population if we include all the inactive owners with bitcoin in exchange wallets from those 15 million Coinbase users and probably 40 million users with the top 25 exchanges - which gives 21.5 million people from the 4.3 billion adults in the world, which ironically is the same number as the private wallets in the world containing $7 of bitcoin or more! Don’t think it could be any more than that, and the true figure for ownership of bitcoin by adults in the world probably lies somewhere between 0.1 and 0.5% I think. Interested in whether you agree we’re in the ballpark or not?