Central banks want to directly influence the real economy: Is this possible?

Central banks in OECD countries increasingly want to intervene in the real economy: In some cases, the nature of the intervention is macroeconomic: the search for full employment, demand stimulus to obtain “overheating”. The question then concerns the conflict of objectives between this real objective and the objective of financial stability (money creation leads to overindebtedness and asset price bubbles); In other cases, the objectives are more microeconomic: support for efficient public investment; support for the energy transition; support for innovative companies, etc. But there are two problems here: An institutional problem: in a democracy, these choices should be made by parliament, not the central bank; An economic problem: if the planned investments are profitable, they may be financed with debt without danger and there is no need for money creation. There remains the case where investments generate large externalities (for example the energy transition) but are insufficiently profitable for the private sector. It is then warranted to internalise the externalities by putting in place incentives, including for example central bank refinancing at more favourable conditions; If the investments are profitable but the country has a large savings shortfall that otherwise prevents them from being financed, financing them with helicopter money may make them possible, but it will increase the external deficit and lead to a risk of excessive external debt. If central banks want to intervene in the real economy, then their main role seems to be to internalise the externalities related to certain investments.