In this article, I show that the key aspects of sovereign debt crises can be rationalized as part of the efficient risk-sharing arrangement between a sovereign borrower and foreign lenders in a production economy with informational and commitment frictions. The constrained efficient allocation involves ex post inefficient outcomes that resemble sovereign default episodes in the data and can be implemented with non-contingent defaultable bonds and active maturity management. Defaults and periods of temporary exclusion from international credit markets happen along the equilibrium path and are essential to supporting the efficient allocation. Furthermore, during debt crises, the maturity composition of debt shifts towards short-term debt and the term premium inverts as in the data.

This article studies the optimal design of rules in a dynamic model when there is a time inconsistency problem and uncertainty about whether the policy maker can commit to follow the rule ex post. The policy maker can either be a commitment type, which can always commit to follow rules, or an optimizing type, which sequentially decides whether to follow rules or not. This type is unobservable to private agents, who learn about it through the actions of the policy maker. Higher beliefs that the policy maker is the commitment type (i.e. the policy maker’s reputation) help promote good behaviour by private agents. We show that in a large class of economies, preserving uncertainty about the policy maker’s type is preferable from an ex ante perspective. If the initial reputation is not too high, the optimal rule is the strictest one that is incentive compatible for the optimizing type. We show that reputational considerations imply that the optimal rule is more lenient than the one that would arise in a static environment. Moreover, opaque rules are preferable to transparent ones if reputation is high enough.

This paper investigates the role of self-fulfilling expectations in sovereign bond markets. We consider a model of sovereign borrowing featuring endogenous debt maturity, risk-averse lenders, and self-fulfilling crises à la Cole and Kehoe (2000). In this environment, interest rate spreads are driven by both fundamental and nonfundamental risk. These two sources of risk have contrasting implications for the maturity structure of debt chosen by the government. Therefore, they can be indirectly inferred by tracking the evolution of debt maturity. We fit the model to Italian data and find that nonfundamental risk played a limited role during the 2008–2012 crisis. (JEL E43, E44, F34, G01, G15, H63)

This article studies the macroeconomic implications of imperfect risk sharing implied by a class of New Keynesian models with heterogeneous agents. The models in this class can be equivalently represented as a representative-agent economy with wedges. These wedges are functions of households’ consumption shares and relative wages, and they identify the key cross-sectional moments that govern the impact of households’ heterogeneity on aggregate variables. We measure the wedges using U.S. household-level data and combine them with a representative-agent economy to perform counterfactuals. We find that deviations from perfect risk sharing implied by this class of models account for only 7% of output volatility on average but can have sizable output effects when nominal interest rates reach their lower bound.

When is financial repression—namely, policies that force banks to hold government debt—optimal? With commitment, such policies are never optimal because they crowd out banks’ productive investments. Without commitment, they are optimal when governments need to issue unusually large amounts of debt, such as during wartime. In such times, repression allows governments to credibly issue more debt. Repression increases credibility because when banks hold government debt, defaults dilute net worth, reduce investment, and are thus costly ex post. Forcing banks to hold debt endogenously increases these ex post costs but has ex ante costs because doing so crowds out investments.