The article explores how the zero lower bound on interest rates affects monetary policy. Using a model, the researchers find that when interest rates are stuck at zero, real interest rates can't drop enough to help the economy during negative spending shocks. This limits the central bank's ability to cushion the impact of these shocks. The level of inflation doesn't have a big impact on this limitation. For small or short-lived shocks, the difference in output between high and low inflation scenarios is small. But for larger and longer-lasting shocks, the impact can be more significant. This suggests that when interest rates are at zero, other tools like fiscal policy may be needed to stimulate the economy.