Klaus Adam

Optimal Monetary Policy under Commitment with a Zero Bound on Nominal Interest Rates

We determine optimal monetary policy under commitment in a forwardlooking New Keynesian model when nominal interest rates are bounded below by zero. The lower bound represents an occasionally binding constraint that causes the model and optimal policy to be nonlinear. A calibration to the U.S. economy suggests that policy should reduce nominal interest rates more aggressively than suggested by a model without lower bound. Rational agents anticipate the possibility of reaching the lower bound in the future and this amplifies the effects of adverse shocks well before the bound is reached. While the empirical magnitude of U.S. mark-up shocks seems too small to entail zero nominal interest rates, shocks affecting the natural real interest rate plausibly lead to a binding lower bound. Under optimal policy, however, this occurs quite infrequently and does not imply positive average inflation rates in equilibrium. Interestingly, the presence of binding real rate shocks alters the policy response to (non-binding) markup shocks.

Discretionary monetary policy and the zero lower bound on nominal interest rates

Ignoring the existence of the zero bound on nominal interest rates one considerably understates the value of monetary commitment in New Keynesian models. A stochastic forward-looking model with an occasionally binding lower bound, calibrated to the U.S. economy, suggests that low values for the natural rate of interest lead to sizeable output losses and deflation under discretionary monetary policy. The fall in output and deflation are much larger than in the case with policy commitment and do not show up at all if the model abstracts from the existence of the lower bound. The welfare losses of discretionary policy increase even further when inflation is partly determined by lagged inflation in the Phillips curve. These results emerge because private sector expectations and the discretionary policy response to these expectations reinforce each other and cause the lower bound to be reached much earlier than under commitment.

Inflation Dynamics and Subjective Expectations in the United States

We estimate a forward looking New Keynesian Phillips Curve (NKPC) for the U.S. using data from the Survey of Professional Forecasters as proxy for expected inflation. We find that the NKPC captures inflation dynamics well, independent from whether output or unit labor costs are used as a measure of marginal costs. We show that identification of expectations exploiting orthogonality to output is severely distorted and explains why the NKPC estimated with survey data performs much better than under rational expectations. We also find that lagged inflation enters the price equation significantly suggesting that there is a role for lagged inflation beyond that of capturing non-rationalities in expectations. Estimating the NKPC of Christiano et al. (2001) where lagged inflation enters due to price indexation by non-reoptimizing firms, we find that it captures the role of lagged inflation reasonably well.

Experimental Evidence on the Persistence of Output and Inflation

This paper presents experimental evidence from a monetary sticky price economy in which output and inflation depend on expected future inflation. With rational inflation expectations, the economy does not generate persistent deviations of output and inflation in response to a monetary shock. In the experimental sessions, however, output and inflation display considerable persistence and regular cyclical patterns. Such behavior emerges because subjects’ inflation expectations fail to be captured by rational expectations functions. Instead, a Restricted Perceptions Equilibrium (RPE), which assumes that agents use optimal but ’simple’ forecast functions, describes subjects’ inflation expectations surprisingly well and explains the observed behavior of output and inflation. JEL Classification: E32, E37, C91

Monetary Conservatism and Fiscal Policy

Does an inflation conservative central bank a la Rogoff (1985) remain desirable in a setting with endogenous fiscal policy? To provide an answer we study monetary and fiscal policy games without commitment in a dynamic stochastic sticky price economy with monopolistic distortions. Monetary policy determines nominal interest rates and fiscal policy provides public goods generating private utility. We find that lack of fiscal commitment gives rise to excessive public spending. The optimal inflation rate internalizing this distortion is positive, but lack of monetary commitment robustly generates too much inflation. A conservative monetary authority thus remains desirable. Exclusive focus on inflation by the central bank recoups large part - in some cases all - of the steady state welfare losses associated with lack of monetary and fiscal commitment. An inflation conservative central bank tends to improve also the conduct of stabilization policy.

LEARNING TO FORECAST AND CYCLICAL BEHAVIOR OF OUTPUT AND INFLATION

This paper considers a sticky price model with a cash-in-advance constraint where agents forecast inflation rates with the help of econometric models. Agents use least squares learning to estimate two competing models of which one is consistent with rational expectations once learning is complete. When past performance governs the choice of forecast model, agents may prefer to use the inconsistent forecast model, which generates an equilibrium where forecasts are inefficient. While average output and inflation result the same as under rational expectations, higher moments differ substantially: output and inflation show persistence, inflation responds sluggishly to nominal disturbances, and the dynamic correlations of output and inflation match U.S. data surprisingly well.

Learning While Searching for the Best Alternative

This paper delovers the solution to an optimal search problem with learning where the searcher has distinguishable search opportunities. The optimal sampling strategy is characterized by simple reservation prices that determine which of the search alternatives to sample and when to stop search.

Learning and Equilibrium Selection in a Monetary Overlapping Generations Model with Sticky Prices

We study adaptive learning in a monetary overlapping generations model with sticky prices and monopolistic competition for the case where learning agents observe current endogenous variables. Observability of current variables is essential for informational consistency of the learning setup with the model setup but generates multiple temporary equilibria when prices are flexible and prevents a straightforward construction of the learning dynamics. Sticky prices overcome this problem by avoiding simultaneity between prices and price expectations. Adaptive learning then robustly selects the determinate (monetary) steady state independent from the degree of imperfect competition. The indeterminate (non-monetary) steady state and non-stationary equilibria are never stable. Stability in a deterministic version of the model may differ because perfect foresight equilibria can be the limit of restricted perceptions equilibria of the stochastic economy with vanishing noise and thereby inherit different stability properties. This discontinuity at the zero variance of shocks suggests to analyze learning in stochastic models.

On the Relation Between Robust and Bayesian Decision Making

This paper compares Bayesian decision theory with robust decision theory where the decision maker optimizes with respect to the worst state realization. For a class of robust decision problems there exists a sequence of Bayesian decision problems whose solution converges towards the robust solution. It is shown that the limiting Bayesian problem displays infinite risk aversion and that decisions are insensitive (robust) to the precise assignment of prior probabilities. This holds independent from whether the preference for robustness is global or restricted to local perturbations around some reference model.

Optimal Trend Inflation

We present a sticky-price model incorporating heterogeneous Firms and systematic firm-level productivity trends. Aggregating the model in closed form, we show that it delivers radically different predictions for the optimal inflation rate than canonical sticky price models featuring homogenous Firms: (1) the optimal steady-state inflation rate generically differs from zero and, (2) inflation optimally responds to productivity disturbances. Using micro data from the US Census Bureau to estimate the inflation-relevant productivity trends at the firm level, we find that the optimal US inflation rate is positive. It was slightly above 2 percent in the year 1986, but continuously declined thereafter, reaching about 1 percent in the year 2013.