A few said it before: no one knows.

I think that 20 % could be possible.

1. In the beginning the coins were pretty worthless, so no one cared about storing them correctly

2. A lot of people (like myself) often lose a key or a stick gets damaged, there are for sure also some lost
   paper wallets.

3. In the future the number will of course grow, because there will be more transactions and more
   people involved in the business. More people more mistakes and losses.