An Evaluation of Friedman's Monetary Instability Hypothesis

In this article, I examine what I call Milton Friedman's Monetary Instability Hypothesis. Drawing on Friedman's work, I argue that there are two main components to this view. The first component is the idea that deviations between the public's demand for money and the supply of money are an important source of economic fluctuations. The second component of this view is that these deviations are primarily caused by fluctuations in the supply of money rather than the demand for money. Each of these components can be tested independently. To do so, I estimate an otherwise standard New Keynesian model, amended to include a money demand function consistent with Friedman's work and a money growth rule, for a period from 1875 to 1963. This structural model allows me to separately identify shocks to the money supply and shocks to money demand. I then use variance decompositions to assess the relative importance of shocks to the supply and demand for money. I find that shocks to the monetary base can account for up to 28% of the fluctuations in output whereas money demand shocks can account for less than 1% of such fluctuations. This provides support for Friedman's view.