Euro zone: The arguments for and against altering the distribution of savings between the fiscal deficit and private investment

There are widespread calls in the euro zone for an increase in fiscal deficit s and public investment, made possible by the low level of interest rates. But this proposal makes sense if it is more efficient to finance public investments than private investments. The fall in interest rates alone does not give any indication as to which type of investment should be increased. Under which scenarios should public investment (the fiscal deficit), as opposed to private investment, clearly be increased in response to low interest rates? When t he marginal return on private capital is low. But this is not the case in the euro zone; When t here are large externalities related to public investment (support for industries of the future, energy transition, education and training). This is the case today in the euro zone.