The quantity theory of money is a theory that the quantity of money matters in income creation. Curiously, this theory may be developed in two mutually exclusive manners. One is by thinking that the quantity of money that matters in income creation is the quantity of money “in” circulation...

In his 2016 paper, Wakabayashi argues:(a) that old Keynesian economics, monetarism, and new Keynesian economics are all equally portfolio adjustment theories, or “stock” approaches to the quantity theory of money; (b) that post-war mainstream macroeconomics has been basically such portfolio...