Let's jump ahead in our on again off again trip down history lane. I promised a multi-part history of the Great Depression and that continues today. Let's just go forward into the 1930s before we return to the 1920s.
The money supply is the product of the monetary base times the money multiplier. Here are the sad pictures from the Great Depression. As you can see on the left, the money supply crashed and burned because on the right, the excess reserve and the currency holding ratios both increased and crashed the money multiplier. The Fed did nothing to the monetary base and the money supply fell by about 33%.