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This thesis consists of three chapters. In the first chapter, titled "Aggregate Risk and Bank Risk-Taking", I propose a general equilibrium model in which strategic interactions between banks and depositors may lead to endogenous bank fragility and a drop in investment and output. With some opacity in bank balance sheets, depositors form expectations about bank risk-taking and demand a return on bank deposits according to their risk. This creates strategic complementarities and possibly multiple equilibria: in response to an increase in funding costs, banks may optimally choose to pursue risky portfolios that undermine their solvency prospects. In a bad equilibrium, bank lending is crowded out by risky asset purchases and weak economic fundamentals lead to a banking crisis. Policy interventions face a trade-o¤ between alleviating banks' funding conditions and strengthening their risk-taking incentives. Due to this trade-off, liquidity provision to banks may eliminate the good equilibrium when it is not targeted. Targeted interventions have the capacity to eliminate the bad equilibrium. The second chapter, titled "Gambling Traps", analyzes macroeconomic dynamics under this framework in a dynamic general equilibrium model. I show that self-fulfilling expectations about high bank risk-taking may lead to 'gambling traps' associated with slow recovery from crises. In a gambling trap, high bank funding costs hinder the accumulation of bank net worth, leading to a prolonged period of financial fragility and a persistent decline in economic activity. I bring this model to bear on the European sovereign debt crisis, in the course of which under-capitalized banks in default-risky countries experienced an increase in funding costs and raised their holdings of domestic government debt. The model is quantified using Portuguese data and accounts for macroeconomic dynamics in Portugal in 2010-2016. Finally, I show that subsidized loans to banks, similar to the European Central Bank's longer-term refinancing operations (LTRO) may perpetuate gambling traps. The third chapter, titled ''Shadow Banking and Market Discipline on Traditional Banks'', is joint work with Matthieu Darracq-Paries, Christo¤er Kok, and Dawid · Zochowski. In this chapter, we present a general equilibrium banking model in which shadow banking arises endogenously and undermines market discipline on traditional banks. We show that depositors' ability to re-optimize in response to crises imposes market discipline on traditional banks: these banks optimally commit to a safe portfolio strategy to prevent early withdrawals. With costly commitment, shadow banking emerges as an alternative banking strategy that combines high risk-taking with early liquidation in times of crisis. We bring the model to bear on the 2007-09 financial crisis in the United States, during which shadow banks experienced a sudden dry-up of funding and liquidated their assets. We derive an equilibrium in which the shadow banking sector expands to a size where its liquidation causes a fire-sale and exposes traditional banks to liquidity risk. Higher deposit rates in compensation for liquidity risk also weaken threats of early withdrawal and traditional banks pursue risky portfolios that may leave them in default. Financial stability is achieved with a tax on shadow bank profits or collateralized liquidity support to traditional banks.

I propose a dynamic general equilibrium model in which strategic interactions between banks and depositors may lead to endogenous bank fragility and slow recovery from crises. When banks' investment decisions are not contractible, depositors form expectations about bank risk-taking and demand a return on deposits according to their risk. This creates strategic complementarities and possibly multiple equilibria: in response to an increase in funding costs, banks may optimally choose to pursue risky portfolios that undermine their solvency prospects. In a bad equilibrium, high funding costs hinder the accumulation of bank net worth, leading to a persistent drop in investment and output. I bring the model to bear on the European sovereign debt crisis, in the course of which under-capitalized banks in default-risky countries experienced an increase in funding costs and raised their holdings of domestic government debt. The model is quantified using Portuguese data and accounts for macroeconomic dynamics in Portugal in 2010-2016. Policy interventions face a trade-off between alleviating banks' funding conditions and strengthening risk-taking incentives. Liquidity provision to banks may eliminate the good equilibrium when not targeted. Targeted interventions have the capacity to eliminate adverse equilibria.

I propose a dynamic general equilibrium model in which strategic interactions between banks and depositors may lead to endogenous bank fragility and slow recovery from crises. When banks' investment decisions are not contractible, depositors form expectations about bank risk-taking and demand a return on deposits according to their risk. This creates strategic complementarities and possibly multiple equilibria: in response to an increase in funding costs, banks may optimally choose to pursue risky portfolios that undermine their solvency prospects. In a bad equilibrium, high funding costs hinder the accumulation of bank net worth and lead to a "gambling trap" with a persistent drop in investment and output. I bring the model to bear on the European sovereign debt crisis, in the course of which under-capitalized banks in default-risky countries experienced an increase in funding costs and raised their holdings of domestic government debt. The model is quantied using Portuguese data and accounts for macroeconomic dynamics in Portugal in 2010-2016. Policy interventions face a trade-off between alleviating banks' funding conditions and strengthening risk-taking incentives. Liquidity provision to banks may perpetuate gambling traps when not targeted. Targeted interventions have the capacity to eliminate adverse equilibria.

I propose a dynamic general equilibrium model in which strategic interactions between banks and depositors may lead to endogenous bank fragility and slow recovery from crises. When banks' investment decisions are not contractible, depositors form expectations about bank risk-taking and demand a return on deposits according to their risk. This creates strategic complementarities and possibly multiple equilibria: in response to an increase in funding costs, banks may optimally choose to pursue risky portfolios that undermine their solvency prospects. In a bad equilibrium, high funding costs hinder the accumulation of bank net worth, leading to a persistent drop in investment and output. I bring the model to bear on the European sovereign debt crisis, in the course of which under-capitalized banks in default-risky countries experienced an increase in funding costs and raised their holdings of domestic government debt. The model is quantified using Portuguese data and accounts for macroeconomic dynamics in Portugal in 2010- 2016. Policy interventions face a trade-o¤ between alleviating banks' funding conditions and strengthening risk-taking incentives. Liquidity provision to banks may eliminate the good equilibrium when not targeted. Targeted interventions have the capacity to eliminate adverse equilibria. ; The ADEMU Working Paper Series is being supported by the European Commission Horizon 2020 European Union funding for Research & Innovation, grant agreement No 649396.

In European countries recently hit by a sovereign debt crisis, the share of domestic sovereign debt held by the national banking system has sharply increased, raising issues in their economic and financial resilience, as well as in policy design. This paper examines these issues by analyzing the banking equilibrium in a model with optimizing banks and depositors. To the extent that sovereign default causes bank losses also independently of their holding of domestic government bonds, under-capitalized banks have an incentive to gamble on these bonds. The optimal reaction by depositors to insolvency risk imposes discipline, but also leaves the economy susceptible to self-fulfilling shifts in sentiments, where sovereign default also causes a banking crisis. Policy interventions face a trade-off between alleviating funding constraints and strengthening incentives to gamble. Liquidity provision to banks may eliminate the good equilibrium when not targeted. Targeted interventions have the capacity to eliminate adverse equilibria.

Cover -- Contents -- 1 Introduction -- 2 A bare-bones model of sovereign debt crises -- 2.1 Optimal default and taxation plans under discretion -- 2.2 Debt pricing -- 2.3 Rational expectations equilibrium and regularity conditions -- 2.4 Equilibria -- 3 The effect of tranching when senior debt is riskless -- 3.1 A Modigliani-Miller irrelevance result -- 3.2 Non-neutrality -- 4 Risky senior debt -- 5 A numerical illustration -- 6 Conclusion -- 7 Appendix -- A Proofs of Propositions -- A.1 Proof of Proposition 1 -- A.2 Proof of Proposition 2 -- A.3 Proof of Proposition 3 -- A.4 Proof of Proposition 4 -- B Equilibria under tranching