how would you define those idle BTC? You see, it is really impossible to tell whether the BTC is just in a cold storage or a paper wallet OR if it is forgotten, destroyed or disposed off (like in a hard disk thrown away to a dump).

The difference is that the ones in a cold storage or a paper wallet can be turned to hot wallet and used in a matter of hours or days, while the bitcoins that were destroyed/disposed off cannot be used ever again.

So I think you wanted to know how many there are bitcoins that were distroyed?

But as I said in the beginning of my post, you cannot distinguish them from the bitcoins in a cold storage, you see.....