I have read from several sources for a long time that more than six million bitcoins are considered lost. Here the figures are clearly understated and obsolete. In principle, how can you accurately calculate the number of already lost bitcoins. It is clear that this figure will always be approximate.

Wow, is it official research or just an article by some make up artist LOL!
I doubt this truth. But whatever it's interesting to research by myself. Thanks!

Same as burnt coin... It's not really a prolem, lots of people lost there privates keys.
Got a bitcoin wallet in 2011 but never retrived my .dat file like lot of people here

That's sad, people never really took bitcoin serious and were careless with their keys. I personally have some small quantity (Less than 1 btc) that I cannot access. I know the wallet but no access

You do realize that the research is based on the addresses being used. According to them my 2014 wallets are probably lost, because I haven't made a single transaction since I bought the coins. I'm sure a lot of coins is lost, but estimating that it's 4 million or 6 million based purely on activity is stupid.
Don't underestimate the hodlers

Its very good to have come across this write-up. It really broadened my mind with much better information about Bitcoin. I also think information like this will be needed on the amount of Bitcoin holders that lost access to their wallet. If at all they are part of the 25% that are lost.

This is just must of the way that bitcoin is lost. And I do believe that much of it was lost in the past because lately, people are very much knowledgeable, wiser and serious with their coin.

It is possible! This is because people die day in and out. When the die, what happens to their bitcoin? If the owners of bitcoin die without leaving any will containing their bitcoin wallet and private key, then the coin will be lost eternally. It is high time we made our next of kins aware of our bitcoin wallet details, death is inevitable.

4 million bitcoins lost and 2 million were hacked that's a lot of bitcoin that are going gone in the market except those stolen ones.

How can it be that he said that these lost bitcoins cannot be part of the supply if there are only limited supply of bitcoin. Lost or not, it's still part of the supply, circulating or not.

Total of 17 million bitcoins on circulation less this 4 million, 13 million bitcoins in the market.

We can't blame them for being careless during the early days if I'm on their shoe probably I'll commit the same mistake.