Comment by puzzledobserver
16 hours ago
In a theoretical sense, you are right.
The life of most currency notes is bank to customer to merchant to bank, and the bank could just track serial numbers to figure out your spending habits.
Practically, it would make little sense. The actual life of most currency notes is bank1 to customer to merchant to bank2, and there is a large probability that bank1 and bank2 are different entities. And then, so many more people use the credit card system, and it is so much easier to track people there, that the ROI on tracking people using cash would be low.
I would be very surprised if any bank tried to scan currency note serial numbers.
Serial number scanning is a common feature of electronic cash counters (also networking!) I'm pretty sure all incoming serial numbers are scanned and checked against a database to find stolen banknotes. I don't know if any banks are tracking outgoing serial numbers, but it would be pretty trivial to implement. I've noticed when I go in and withdraw cash from a human teller that the cash no longer comes from a drawer, but rather is dispensed by an automatic cash handling machine and then handed to me.
Is the probability that large for bank1 vs bank2? There’s only a few major banks left. Chase has so many ATMs it’s hard to compete with the access.