Stabilizing non-fundamental asset price movements under discretion and limited information

Inflation, output and interest rate stabilization are all potential central bank objectives. We explore whether monetary policy should respond to asset price fluctuations when they are driven by irrational expectational shocks to the future returns to capital. In our model, an optimistic shock to future returns generates both an increase in equity prices and physical investment. The increased investment is inefficient and, thus, a central bank optimally responds to this expectations shocks. This induces a trade-off between stabilizing nominal prices and non-fundamental asset price movements. We compare the optimal policy under different assumptions: full versus limited information and commitment versus discretion. If the central bank has limited information about whether an asset price movement has a fundamental or non-fundamental origin, then the central bank responds less aggressively to the non-fundamental exuberance shocks than under full information. Without commitment, a central bank responds more aggressively to non-fundamental exuberance shocks.