The lack of effectiveness of expansionary monetary policies has led to the appearance of new heterodox theories

We look at the examples of the United States and the euro zone. The highly expansionary monetary policies that have been conducted have had little impact on inflation, credit and asset prices, and therefore altogether on the macroeconomic equilibrium. This observation has given rise to new heterodox theories: The fact that an expansionary monetary policy does not bring back inflation has given rise to Neo- Fisherism , the theory according to which the nominal interest rate determines inflation in the long term. Persistently low nominal interest rates therefore lead to low inflation; The fact that an expansionary monetary policy has a limited impact on credit, asset prices and therefore real activity and that fiscal policy therefore is more effective than monetary policy in stimulating activity has given rise to: The "helicopter money" theory: money creation must be targeted by distributing money to the economic agents whose spending one wants to boost; Modern monetary theory (MMT): fiscal policy should be used to maintain full employment permanently, and the fiscal deficit should be financed by money creation to prevent interest rates from rising. These theories heterodox stimulate thinking: If nominal interest rates are low, how can the Fisher equation be complied with in the long term? What is the difference between helicopter money and quantitative easing? What are the risks associated with the use of modern monetary theory?