Kieran James Walsh

Policy Analysis Using DSGE Models: An Introduction

Many central banks have come to rely on dynamic stochastic general equilibrium, or DSGE, models to inform their economic outlook and to help formulate their policy strategies. But while their use is familiar to policymakers and academics, these models are typically not well known outside these circles. This article introduces the basic structure, logic, and application of the DSGE framework to a broader public by providing an example of its use in monetary policy analysis. The authors present and estimate a simple New Keynesian DSGE model, highlighting the core features that this basic specification shares with more elaborate versions. They then apply the estimated model to study the sources of the sudden increase in inflation that occurred in the first half of 2004. One important lesson derived from this exercise is that the management of expectations can be a more effective tool for stabilizing inflation than actual movements in the policy rate. This result is consistent with the increasing focus on the pronouncements of central bankers regarding their future actions.

The Double Power Law in Consumption and Implications for Testing Euler Equations

We provide evidence suggesting that the cross-sectional distributions of US consumption and its growth rate obey the power law in both the upper and lower tails, with exponents approximately equal to four. Consequently, high-order moments are unlikely to exist, and the generalized method of moments estimation of Euler equations that employs cross-sectional moments may be inconsistent. Through bootstrap studies, we find that the power law appears to generate spurious nonrejection of heterogeneous-agent asset pricing models in explaining the equity premium. Dividing households into age groups, we propose an estimation approach that appears less susceptible to fat tail issues.

Uniqueness and Stability of Equilibrium in Economies with Two Goods

We offer new sufficient conditions ensuring demand is downward sloping local to equilibrium. It follows that equilibrium is unique and stable in the sense that rising supply implies falling prices. In our setting, there are two goods, which we interpret as consumption in different time periods, and many impatience types. Agents have the same Bernoulli utility function, but the types differ arbitrarily in time preference. Our main result is that if endowments are identical and utility displays nonincreasing absolute risk aversion, then market demand is strictly downward sloping local to equilibrium. We discuss implications for the Diamond-Dybvig literature.

Inefficient Liquidity Provision

We prove that in competitive market economies with no insurance for idiosyncratic risks, agents will always overinvest in illiquid long term assets and underinvest in short term liquid assets. We take as our setting the seminal model of Diamond and Dybvig (1983), who Orst posed the question in a tractable model. We reach such a simple conclusion under mild conditions because we stick to the basic competitive market framework, avoiding the banks and intermediaries that Diamond and Dybvig and others introduced.

A Theory of Portfolio Choice and Partial Default

I develop a portfolio choice model that allows for partial default and accommodates trade in a rich set of assets. I characterize the solution to an infinite horizon, consumption/portfolio problem with Markov shocks and many assets. The characterization facilitates a simple solution algorithm and allows me to establish properties of the model. For example, agents default more in bad economic times. I define Recursive Default Equilibrium, which extends the equilibrium concept of Dubey, Geanakoplos, and Shubik (2005) to include an infinite number of time periods and many assets. I prove existence for a tremble-refined equilibrium that rules out off-equilibrium pessimism.

Credibility and Credulity: How Beliefs about Beliefs Affect Entry Incentives

In this note we investigate the infringement (entry) decision for a firm facing an incumbent patent holder with uncertain patent rights. The entrant risks a dispute by entering, resulting in either a settlement (licensing) or litigation and trial. Using the litigation model described by Priest and Klein, we investigate the expected dispute resolution and its impacts on the entrants pre-dispute behavior. The primary contribution is to show that the entrants expectations about the patent holders beliefs about patent enforceability are a driving factor behind the entry decision. We develop a simple taxonomy of entrant and incumbent types to explain the entry decision.

The Equity Premium and the One Percent

We show that in a general equilibrium model with heterogeneity in risk aversion or belief, shifting wealth from an agent who holds comparatively fewer stocks to one who holds more reduces the equity premium. Since empirically the rich hold more stocks than do the poor, the top income share should predict subsequent excess stock market returns. Consistent with our theory, we find that when the income share of top earners in the U.S. rises, subsequent one year excess market returns significantly decline. This negative relation is robust to (i) controlling for classic return predictors such as the price-dividend and consumption-wealth ratios, (ii) predicting out-of-sample, and (iii) instrumenting with changes in estate tax rates. Cross-country panel regressions suggest that the inverse relation between inequality and returns also holds outside of the U.S., with stronger results in relatively closed economies (emerging markets) than in small open economies (Europe).

Spending Shocks and Interest Rates

Most macroeconomic models imply that increases in government spending cause interest rates to rise, but empirical evidence from the U.S. generally fails to support this prediction. We propose a novel explanation for how government spending can have a muted or negative temporary effect on interest rates: the increased supply of loans associated with government spending is offset by an increase in the demand for loans due to higher aggregate income. We demonstrate this mechanism theoretically and provide evidence consistent with the models predictions.

Fat Tails and Spurious Estimation of Consumption-Based Asset Pricing Models

The standard generalized method of moments (GMM) estimation of Euler equations in heterogeneous-agent consumption-based asset pricing models is inconsistent under fat tails because the GMM criterion is asymptotically random. To illustrate this, we generate asset returns and consumption data from an incomplete-market dynamic general equilibrium model that is analytically solvable and exhibits power laws in consumption. Monte Carlo experiments suggest that the standard GMM estimation is inconsistent and susceptible to Type II errors (incorrect non-rejection of false models). Estimating an overidentified model by dividing agents into age cohorts appears to mitigate Type I and II errors.