This article studies the impact of a credit expansion monetary policy on output and unemployment rate. In the introduction the history of the Phillips curve and its interpretation are presented to understand why New Consensus Macroeconomics argues that monetary policy is neutral in long-run i. e. has no effect on economic activity and natural unemployment rate. This New Consensus Macroeconomics supports the independence of the Central Bank, inflation-targeting and the strategy of constrained discretion model and influences strongly the monetary policy of central bank today. The second section critics these three principles of the new consensus. It opposes free-banking to central banking system, and takes the defense of deflation to critic the inflation-targeting. Then the third section deals with long-run neutrality of monetary policy. In an Austrian Business Cycle perspective, there is neutrality of monetary only if the production structure must always return exactly to its level of before the boom. It is improbable, because the monetary policy via tax inflation and artificial variation of real interest rate has a long-run effects on the conditions of financing of entrepreneurial project and in fine all the market process dynamic.