Fun thing, I looked it up for banknotes. Turns out there are only 15 billion euro banknotes. Fits in a Postgres database! Most of the cycles are extremely short

Fun thing, I looked it up for banknotes. Turns out there are only 15 billion euro banknotes. Fits in a Postgres database! Most of the cycles are extremely short: Withdraw at the ATM, pay at the bakery, back to the bank. If banks took note of note numbers, it would probably be straightforward to trace 80% of the transactions. And trace banknotes that stayed 6 months offline, and those that are always withdrawn by someone and used in a specific suburb (=possible drug deal), especially when he pays everything else with credit card. Of course it is 20x less efficient than tracking Bitcoins, and requires input sources from several places, but it’s fun to know that even banknotes are quite easily traceable.