The euro zone: What will be the effects of negative real interest rates?

Real interest rates have been clearly negative in the recent period in the euro zone. What consequences can be expected of these negative real interest rates? There are two opposing views: The neo-Fisherian theory: in the long run real interest rates must return to an exogenous level, related to technological progress and potential growth . There will therefore be a decline in inflation until this rebalancing of real interest rates is completed . In neo-Fisherian theory, long-term inflation is therefore determined by nominal interest rates; The "optimistic" theory of adjustment of the capital stock: negative real interest rates will lead to additional capital accumulation in the euro zone until the marginal productivity of capital is equal to the real interest rate . According to this theory, there will be a sharp rise in investment in the euro zone. The ECB is definitely not neo-Fisherian.