How could those stats ever be verified? Report was probably issued from a think tank who gets its funding from Wall Street banks...
It's the blockchain. You can count the amount of coins moving easily enough. Just add up the value.
I assume the vast majority of it is just coins moving around between wallets, exchanges and gambling sites.
I think he means how did the OP validate all if his percentages? The purpose if each transaction is not tracked on the blockchain (of course).