The percentage of bitcoin in circulation reached a low of 60% during summer 2017 and now stands at 70%.
Suggesting about 30% of all coins mined so far, circa 5 million, may have been lost forever.
In 2014, 80% of all coins circulated in a three years time-frame according to blockchain data from Santiment’s Valentin Mihov who says as coins are getting lost and locked, the percentage has dropped.
It is suggested Satoshi Nakamoto mined one million bitcoin which has not moved since. In addition, there may be small amounts of coins that are lower in value than the current transaction fee.
Such dust coins can likewise be considered as lost with circa 25,000 BTC at dust like values on-chain.
Far more important might be small amounts on exchanges that are effectively forgotten with an estimate there difficult to provide.
Then we’ve all heard that story of the hard-drive full of bitcoin thrown away because initially bitcoins were mineable on your laptop by just clicking a button. So they were kind of given out for free and didn’t have much value.
Just how many were discarded at that point is not very clear, but there were also coding errors where bugs would send the coins to an unrecoverable address. The known sums there are small though, about 2,000 BTC or so.
Then there’s the lost of private keys due to potentially many reasons. Someone must have forgotten it in their pocket, for example, and perhaps washed it out.
Now obviously people take a lot more care, but for some aspects there isn’t much you can do, like dust which is small in individual cases but adds up when combined.
Meaning bitcoin doesn’t quite have a fixed quantity, but a decreasing quantity. There are however a lot of zeros behind one bitcoin, but at some point it may be the case that even 1 satoshi is a rarity.
In a millennium perhaps because for the next century, new coins will continue to be generated, although at a decreasing rate with inflation falling not far from zero in 2024 and to less than 2% next year.