Here's the evidence from Tim Sablik in "Is Cash Still King?" written for Econ Focus from the Federal Reserve Bank of Richmond (Second Quarter 2018, pp. 18-21). Back in the 1990s and into the first decade of the 2000s, $1 bills were most common, with $20s in second place. (This ranking accurately represents my own wallet, for what it's worth!). But $100s have growth steadily and taken over first place.
Indeed, the total value of US currency in circulation has been rising over time, but most of that gain in value is due to the rise in $100 bills.
Clearly, there is a puzzle here. As Sablik points out, evidence from consumer surveys finds that cash is used for about 27% of transactions in the last decade or so, but mostly for small purchases. It seems unlikely that the number of $100 bills in circulation is about typical consumers making typical purchases. In round numbers, the 12 billion $100 bills in circulation divided by a US population of 325 million implies that on average, every person in the US has 37 $100 bills in their possession. The total amount of US cash in circulation works out to about $4,800 for every person in the US. (This does not accurately represent the contents of my wallet.)
The standard explanation is that a considerable amount of US currency is being used outside the US, both as a medium of exchange and as a store of value. Some proportion of that amount--no one really knows how much--is surely helping to facilitate illegal activities. There are ongoing proposals to eliminate large-denomination bills: Sablik points out that the European Union ended production of 500-euro notes in 2016.
For some previous posts on the subject, see:
- "Eliminate High-Denomination Bills?" (March 18, 2016)
- "Who is Holding the Large Denomination Bills? (August 11, 2014)
- "The Soaring Number of $100 Bills" (June 10, 2013)