This is the most important graph explaining the US economy. Velocity is GDP divided by the money supply. A decline in velocity has the same effect as a decline in the money supply--deflation, low interest rates, slow GDP growth etc. 
It's important because it's about to get a lot worse as GDP falls due to the effects of the virus and the Fed tries to keep the financial system from collapsing by raising the money supply. This means velocity will far further from an already low base.
I explain this in more detail in this article. Scroll ahead to the subhead, "Supply Slide." thebaffler.com/salvos/right-i…
Velocity is basically the speed at which money is spent, how many times each dollar turns over in the economy. Rising velocity affects the economy like a higher money supply, lower velocity is like a shrinkage of the money supply.
A shrinkage of the money supply was the root cause of the Great Depression. This used to be what all conservative economists believed because it was one of the great theories of Milton Friedman. A fall in velocity was the root cause of the Great Recession, 2008-2009 - present.
fall further
