[alcover]

> tracking of this information down to that level would be pretty pointless

Maybe pretty pointfull tracking shadow economy. When Bob sells moonlight stuff his clients will more often than not simply go to the ATM, withdraw the sum and hand it to him. Bob will then buy at shop with big bill. Shop owner will deposit bill at bank..

[jjk166]

And how do you know which bill from the shop is Bob's? Or which hands the bill passed through before or after going through Bob? The only thing you'll be able to determine is that some of the money withdrawn from the local atms eventually gets spent at the local shops, which you could probably intuit.