I wonder how we determine similar 'activity' as far as normal currencies are concerned? Either it's related to money moving between accounts, or it's related to

I wonder how we determine similar 'activity' as far as normal currencies are concerned? Either it's related to money moving between accounts, or it's related to volumes on an exchange, or something else entirely, but surely those values are just as easily 'manipulated' as any of BTC. Admittedly the volumes themselves dictate that me moving money from one bank account to another will have less of an impact on the final number, but then again, I'm always moving money between my different bank accounts, but never between my Bitcoin addresses. I obviously can't say for certain, but I don't think there's a meaningful number of users moving BTC between their wallets for no reason.