Oddly - cash can be, and appears to be, widely tracked. Many ATMs scan serial numbers of bills, and network analysis of that data can be VERY informative.
Do you have a source? How valuable is knowing the serial number of an ATM dispensed bill?
Very little cash is deposited into an ATM. Any time I’ve deposited cash I’ve never seen it scanned (it goes into the drawer).
And if it were scanned at multiple points think of the cash in a register at a store? How many transactions does it go through before getting scanned again? Especially smaller bills?
Seeing that a bill was dispensed at an ATM on Market St in San Francisco then deposited by a restaurant in San Mateo 1 month later tells you what exactly?
IIRC research showed that most large bills really were in circulation for 1 transaction only. As in, withdrawn from ATM, paid for something, deposited by the merchant at the end of the same day. Only small bills given out as change stay in circulation; but small bills constitute a tiny fraction of the total money circulation.
Up to the bank as to what level of detail they record and where the data goes, but the sensors are usually there.
If you know 100 people pulled cash out of various amounts over time, and 1 person deposited $100 from each of them - that tells you 100 people all made nearly the same purchase of something around $100 from that person correct?
Even better if some portion of those funds sometimes end up in someone else’s pocket.
It’s mainly useful for detecting black and grey market activity, like someone selling drugs or sex work or whatever, and people working with them directly. Look at it
Over long enough and you could probably identify almost
all of the business associates and regular customers.
Same tricks are used to track Bitcoin.
That said, not usually worth it for anyone to do this, and it isn’t disclosed how common scanning or tracking this way is done (and some banks deny it), so your mileage may vary depending on your level of paranoia.
The great thing about cash is you can use it everywhere, not just for things you want to keep on the down low.
You take that fat stack of bills you made selling dime bags and you go to Walmart and you buy groceries with it or whatever. Only the things that require a non-cash method of payment need to involve the banking system. Even then you can buy prepaid visa gift cards to handle most of those case if you're ok with the inconvenience.
Some merchants can deposit their cash through certain ATMs. Maybe they scan cash confiscated from criminals.
Getting insight from someone's cash transaction over time, in aggregate, is an excercise in statistics and probably yields many interesting and surprising results.
