if —that is, if and only if Thus the monetary authority would have to be sufficiently astute in its policy timing, in trying to counteract anticipated fluctuations in velocity, that the correlation of its money supply changes with velocity changes is not merely negative, but sufficiently negative to overcome the inherently GDP-variance-magnifying effects of money supply variation. Friedman believed that this condition for discretionary policy to be stabilizing is unlikely to be fulfilled in practice, because of the timing problems discussed above. A related issue is the probable existence of multiplier uncertainty—imperfect knowledge of the overall ultimate effect of a policy action of a given size. Generally multiplier uncertainty calls for more caution and the use of quantitatively smaller policy actions. Arguments for Proponents of the use of discretionary policy, including in particular Keynesians, argue that our understanding of the workings of the economy is sufficiently astute, and the accessibility of detailed real-time economic data to policymakers is sufficiently great, that in practice discretionary policy has been stabilizing. For example, it is widely believed that the extreme expansion of the monetary base by the U.S. Federal Reserve and other central banks prevented the Great Recession of the 2000s decade from becoming a full-blown depression. References Monetary policy Fiscal policy