learning

August 1, 2010

Uncertainty about the riskiness of a new financial environment was an important factor behind the U.S. credit crisis. We show that a boom-bust cycle in debt, asset prices and consumption characterizes the equilibrium dynamics of a model with a collateral constraint in which agents learn "by observation" the true riskiness of the new environment. Early realizations of states with high ability to leverage assets into debt turn agents overly optimistic about the probability of persistence of a high-leverage regime. Conversely, the first realization of the low-leverage state turns agents unduly pessimistic about future credit prospects. These effects interact with the Fisherian deflation mechanism, resulting in changes in debt, leverage, and asset prices larger than predicted under either rational expectations without learning or with learning but without Fisherian deflation. The model can account for 69 percent of the rise in net household debt and 53 percent of the rise in residential land prices between 1997 and 2006, and it predicts a sharp collapse in 2007.

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January 1, 2005

Central bankers frequently emphasize the critical importance of anchoring private inflation expectations for successful monetary policy and macroeconomic stabilization. In most monetary policy models, however, expectations are already anchored through the assumption of rational expectations and perfect knowledge of the economy. In this Paper, we re-examine the role of inflation expectations by positing, instead, that agents have imperfect knowledge of the precise structure of the economy and policy-makers' preferences, and rely on a perpetual learning technology to form expectations. We find that with learning, disturbances can give rise to endogenous inflation scares, that is, significant and persistent deviations of inflation expectations from those implied by rational expectations, even at long horizons. The presence of learning increases the sensitivity of inflation expectations and the term structure of interest rates to economic shocks, in line with the empirical evidence. We also explore the role of private inflation expectations for the conduct of efficient monetary policy. Under rational expectations, inflation expectations equal a linear combination of macroeconomic variables and as such provide no additional information to the policy-maker. In contrast, under learning, private inflation expectations follow a time-varying process and provide useful information for the conduct of monetary policy.

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