This paper studies optimal monetary policy in a model where aggregate fluctuations are driven by the private sector's uncertainty about the economy's fundamentals. Information on aggregate productivity is dispersed across agents and there are two aggregate shocks: a standard productivity shock and a “noise shock” affecting public beliefs about aggregate productivity. Neither the central bank nor individual agents can distinguish the two shocks when they are realized. Despite the lack of superior information, monetary policy can affect the economy's relative response to the two shocks. As time passes, better information on past fundamentals becomes available. The central bank can then adopt a backward-looking policy rule, based on more precise information about past shocks. By announcing its response to future information, the central bank can influence the expected real interest rate faced by forward-looking consumers with different beliefs and thus affect the equilibrium allocation. If the announced future response is sufficiently aggressive, the central bank can completely eliminate the effect of noise shocks. However, this policy is typically suboptimal, as it leads to an excessively compressed distribution of relative prices. The optimal monetary policy balances the benefits of aggregate stabilization with the costs in terms of cross-sectional efficiency.

This paper studies the welfare properties of competitive equilibria in an economy with financial frictions hit by aggregate shocks. In particular, it shows that competitive financial contracts can result in excessive borrowing ex ante and excessive volatility ex post. Even though from a first-best perspective the equilibrium always displays under-borrowing, from a second-best point of view excessive borrowing can arise. The inefficiency is due to the combination of limited commitment in financial contracts and the fact that asset prices are determined in a spot market. This generates a pecuniary externality that is not internalized in private contracts. The model provides a framework to evaluate preventive policies, which can be used during a credit boom to reduce the expected costs of a financial crisis.

This paper presents a model of business cycles driven by shocks to consumer expectations regarding aggregate productivity. Agents are hit by heterogeneous productivity shocks, they observe their own productivity and a noisy public signal regarding aggregate productivity. The public signal gives rise to “noise shocks,” which have the features of aggregate demand shocks: they increase output, employment, and inflation in the short run and have no effects in the long run. Numerical examples suggest that the model can generate sizable amounts of noise-driven volatility.

We study the effects of a credit crunch on consumer spending in a heterogeneous-agent incomplete-market model. After an unexpected permanent tightening in consumers’ borrowing capacity, constrained consumers are forced to repay their debt, and unconstrained consumers increase their precautionary savings. This depresses interest rates, especially in the short run, and generates an output drop, even with flexible prices. The output drop is larger with sticky prices, if the zero lower bound prevents the interest rate from adjusting downward. Adding durable goods to the model, households take larger debt positions and the output response can be larger.

In this paper, we build a model where the presence of liquidity constraints tends to magnify the economy's response to aggregate shocks. We consider a decentralized model of trade, where agents may use money or credit to buy goods. When agents do not have access to credit and the real value of money balances is low, agents are more likely to be liquidity constrained. This makes them more concerned about their short-term earning prospects when making their consumption decisions and about their short-term spending opportunities when making their production decisions. This generates a coordination element in spending and production which leads to greater aggregate volatility and greater comovement across producers.

We characterize equilibria with endogenous debt constraints for a general equilibrium econ-omy with limited commitment in which the only consequence of default is losing the ability to borrow in future periods. First, we show that equilibrium debt limits must satisfy a simple con-dition that allows agents to exactly roll over existing debt period by period. Second, we provide an equivalence result, whereby the resulting set of equilibrium allocations with self-enforcing private debt is equivalent to the allocations that are sustained with unbacked public debt or rational bubbles. In contrast to the classic result by Bulow and Rogo § (AER, 1989), positive levels of debt are sustainable in our environment because the interest rate is su¢ciently low to provide repayment incentives. We thank for useful comments the editor, Harald Uhlig, three anonymous referees, Marios Angeletos, Andy

Foreign currency debt is considered a source of financial instability in emerging markets. We propose a theory in which liability dollarization arises from an insurance motive of domestic savers. Since financial crises are associated to depreciations, savers ask for a risk premium when saving in local currency. This force makes domestic currency debt expensive, and incentivizes borrowers to issue foreign currency debt. Providing ex post support to borrowers can alleviate the effect of the crisis on savers’ income, lowering their demand for insurance, and, surprisingly, it can reduce ex ante incentives to borrow in foreign currency.

We study slow moving debt crises: self-fulfilling equilibria in which high interest rates, due to the fear of a future default, lead to a gradual but faster accumulation of debt, ultimately validating investors’ fear. We show that slow moving crises arise in a variety of settings, both when fiscal policy follows a given rule and when it is chosen by an optimizing government. A key assumption, in all these settings, is that the borrowing government cannot commit to issue a fixed amount of bonds in a given period. We discuss how multiplicity is avoided for low debt levels, for sufficiently responsive fiscal policy rules, and for long enough debt maturities. When the equilibrium is unique, debt dynamics are characterized by a tipping point, below which debt falls and stabilizes and above which debt and default rates grow.

Financial crises typically occur because firms and financial institutions are highly exposed to aggregate shocks. We propose a theory to explain these exposures. We study a model where entrepreneurs can issue state-contingent claims to consumers. Even though entrepreneurs can use these instruments to hedge negative shocks, they do not necessarily do so because insuring against these shocks is expensive, as consumers are also harmed by them. This effect is self-reinforcing because riskier balance sheets for entrepreneurs imply higher income volatility for the consumers, making insurance more costly in equilibrium. We show that this feedback is quantitatively important and leads to inefficiently high risk exposure for entrepreneurs.

The paper studies how asset prices are determined in a decentralized market with asymmetric information about asset values. We consider an economy in which a large number of agents trade two assets in bilateral meetings. A fraction of the agents has private information about the asset values. We show that, over time, uninformed agents can elicit information from their trading partners by making small offers. This form of experimentation allows the uninformed agents to acquire information as long as there are potential gains from trade in the economy. As a consequence, the economy converges to a Pareto efficient allocation.