So....you want conspiracy theory. In the US bills a have a metalic strip in them. Stores have sensors at the exits that "monitor theft", but I hear that they also count your money in your wallet. Why you ask, because the banks are trying to get everybody off of cash and on to plastic because they make money every time your card is swiped. I don't personally believe that BS but I had a boss that did. As a result he would pull the strip out of every bill he ever got. What a nut job.