Do interest rates have an effect on the savings-investment equilibrium?

A key objective of monetary policy is normally to adjust savings and investment. In countries with excess savings, monetary policy should become expansionary (reduction in interest rates) to discourage savings (by the private sector) and stimulate investment; in countries with a savings shortfall, monetary policy should generally become restrictive (increase in interest rates) to boost savings (by the private sector) and curb investment. But actual developments in the United States, the euro zone and Japan show that monetary policy has only a very small or even non-existent effect on the savings-investment equilibrium. This reveals the ineffectiveness of monetary policy both at preventing deflation and at preventing a chronic external deficit.