I ran across this story about Canadian counterfeiters, and I was interested because of the quote below,
“Because the polymer series’ notes are so secure … there’s almost an overconfidence among retailers and the public in terms of when you sort of see the strip, the polymer looking materials, everybody says ‘oh, this one’s going to be good because you know it’s impossible to counterfeit,'” he said.
“So people don’t actually check it.”
which is an interesting comment on the mindset of people. If you’ve read Surely You’re Joking, Mr. Feynman you might see there’s some similar commentary on people thinking things were safe just because (there’s a safe, or a fence) but when it came down to the details, people were pretty stupid about actually leveraging the features that would have made the systems secure. (Though Feynman explains it from a different perspective than that).
With this presumably false sense of security, there are actually some counterfeit bills in the system
Pound said since the polymer series was announced in 2011, police have confirmed 56 polymer counterfeit notes across Canada, out of about 500-million polymer notes in circulation.
But then it occurred to me that the article didn’t actually mention any context for these numbers, and context is important. Is the system failing — is ten bills out of a million a big number? With a little searching I ran across an even more interesting article on how Canada got to the point where they decided to use polymer (don’t call it plastic!) currency.
By  Canada’s counterfeit rate had ballooned to 470 PPM. That year alone, 552,692 forged banknotes were passed, a record number. Canada’s PPM level was as much as 100 times the ratio of some G20 countries.
Which means that the
10 PPM 0.1 PPM for the polymer bills is a huge improvement and even lower than Canada’s rate in 1990, which was just 4 PPM. The article says that 50 PPM is considered the threshold for having a counterfeiting problem. So while the complacency might be a problem, the new system is working pretty well.
edit: Fixed the last paragraph. A little mathlexia.