Not the deepest bit of journalism you'll find on our monetary system. He leaves out quite a bit; money creation other than printing, measurement (M0, M1, ...), and a complete picture on how the Fed attempts to (or believes it can) control money supply.
Although I agree that the issue of money supply is not described well here, it's not a very long article, nor is it really aiming to explain all that.
I think it's fun to see the average lifespan of bills. Who'd'a thunk that most small ones are in use for less than 5 years??
I noticed that they left out $2 bills. Many people save them for some reason (they're lucky! they're rare!) and some of the charts showing lifespans that include $2 bills show their lifespan about 10x the life of other bills.
