Thank you for this interesting graph!
However I'm quite sceptical about the zombie coin estimate. I think the estimate is much too high.
For the purposes of this article a ‘zombie bitcoin’ is defined as all bitcoins associated with a public key address which has had no send transactions for over 18 months. Why 18 months? Because today bitcoins are worth about $600 apiece, and back in December of 2013 they were worth over $1,000 apiece. Anyone who owned bitcoins prior to 18 months ago would have acquired them at a maximum cost basis of probably about $30, and that is estimating very high. Much more likely most had a cost basis of under $10, and the average overall is well under $1. You would need to have incredible willpower to resist a 4,000% or even astronomically higher return on an investment.
The definition in the article seems rather arbitrary and the arguments do not convince me. I don't see a reason to assume that people will sell Bitcoin for fiat money when they realize Bitcoin is the future and that Bitcoin has shown its viability as a store of value by appreciating against inflationary fiat money. Assuming that Bitcoiners behave like investors in the stockmarket is not reasonable, because many Bitcoiners show an extremely strong ideological attachment to *their* currency.
Only coins where loss of the private keys is proven should be classified as zombie coins.
ya.ya.yo!