I think number of unspendable bitcoin is more than this because there are also lots of addresses which contain bitcoins and nobody have access to it, like addresses of wallets whose password were lost, known addresses of satoshi etc. However nice listing...
That's true, but there is no way to confirm that they are really lost, or that the people in question really haven't access to their coins anymore. That's why it's better to wait and not include them into compiled "lost coins" lists. I from time to time spend some hours on analyzing very old wallet addresses containing plenty of coins. In some cases you will see that after 5 or 6 years the person behind one of these addresses starts moving his coins. That's why I never take for granted that they lost access to their wallets.
that is a good research. if so, then probably the owners of the addresses hold their bitcoin until some period of time. and then they will move the coins, probably they sell it. so in this case, we just need to wait for 5-6 years to know that the coins in the wallet are really lost or not yet.