We present a signalling theory of Quantitative Easing (QE) at the zero lower bound on the short term nominal interest rate. QE is effective because it generates a credible signal of low future real interest rates in a time consistent equilibrium. We show these results in two models. One has coordinated monetary and fiscal policy. The other an independent central bank with balance sheet concerns. Numerical experiments show that the signalling effect can be substantial in both models.
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