Edouard Challe

Episodes of low natural interest rates, even transitory, pose a challenge to monetary policy, by possibly causing the effective lower bound (ELB) on the policy rate to bind. Those episodes are more likely to occur not only when the natural rate is low on average but also when fluctuations around its average level are large. We study the responsiveness of the natural interest rate to structural aggregate shocks affecting the aggregate supply of and demand for savings. Using a quantitative overlapping-generations model, we trace back this responsiveness to the slopes of aggregate savings supply and demand curves and argue that both curves have likely flattened over the past four decades in the US This implies a greater sensitivity of the natural interest rate to structural shocks affecting the supply of and demand for aggregate savings – making it more likely, all else equal, that it fall into negative territory.

We study optimal monetary policy in an analytically tractable heterogeneous agent New Keynesian model with rich cross-sectional heterogeneity. Optimal policy differs from a representative agent benchmark because monetary policy can affect consumption inequality, by stabilizing consumption risk arising from both idiosyncratic shocks and unequal exposures to aggregate shocks. The trade-off between consumption inequality, productive efficiency, and price stability is summarized in a simple linear-quadratic problem yielding interpretable target criteria. Stabilizing consumption inequality requires putting some weight on stabilizing the level of output, and correspondingly reducing the weights on the output gap and price level relative to the representative agent benchmark.

I study optimal monetary policy in a sticky-price economy wherein households precautionary-save against uninsured, endogenous unemployment risk. In this economy greater unemployment risk raises desired savings, causing aggregate demand to fall and feed back to greater unemployment risk. This deflationary spiral is constrained inefficient and calls for an accommodative monetary policy response: after a contractionary aggregate shock the policy rate should be kept significantly lower and for longer than in the perfect-insurance benchmark. For example, the usual prescription obtained under perfect insurance of a hike in the policy rate in the face of a bad supply (i.e., productivity or cost-push) shock is easily overturned. The optimal policy breaks the deflationary spiral and takes the dynamics of the imperfect-insurance economy close to that of the perfect-insurance benchmark. These results are derived in an economy with zero asset supply (zero liquidity) and are thus independent of any redistributive effect of monetary policy on household wealth.

We construct, and then estimate by maximum likelihood, a tractable dynamic stochastic general equilibrium model with incomplete insurance and heterogenous agents. The key feature of our framework is that cross‐sectional heterogeneity remains finite dimensional. The solution to the model thus admits a state‐space representation that can be used to recover the distribution of the model’s parameters. Household heterogeneity expands the set of observables to cross‐sectional moments available at the business‐cycle frequency (in addition to the usual macro and monetary time series). Incomplete insurance gives rise to a precautionary motive for holding wealth that propagates aggregate shocks via (i) a stabilizing aggregate supply effect, working through the supply of capital, and (ii) a destabilizing aggregate demand effect coming from the feedback loop between unemployment risk and precautionary saving. Using the estimated model to measure the contribution of precautionary savings to the propagation of recent recessions, we find strong aggregate demand effects during the Great Recession and, to a lesser extent, during the 1990–1991 recession. In contrast, the supply effect at least offsets the demand effect during the 2001 recession.