I know it is a tricky question. What do you think, how many Bitcoins are lost forever and are 'out of the network' by lost private keys?
difficult question , there is not person calculate .
but i think very many because users bitcoin many too
I think there will be many people who lost their bitcoin but a variety of reasons. for reasons lost because people have taken private key, I think only a few people who have, I've never lost bitcoin for that reason