<p>In this thesis I explore dimensions through which changes in expectations can serve as a driver of business cycles in a rational expectations setting. Exploiting both the ``sunspot'' and ``news-shock'' approaches to expectations-driven business cycles, I use various theoretical models to investigate how changes in expectations may have played a role in macroeconomic events such as the technological revolution of the 1990's and the financial boom and bust of 2003-2008.</p> <p>In the first chapter, I explore the ability of a model with knowledge capital to generate business cycles driven by expectations of future movement in total factor productivity (TFP). I model knowledge capital as an input into production which is endogenously produced through a learning-by-doing process. When firms receive news of an impending productivity increase, the value of knowledge capital rises, inducing the firm to hire more hours to ``invest'' in knowledge capital. The rise in the value of knowledge capital immediately raises the value of the firm, causing an appreciation in stock prices. If the expected increase in productivity fails to materialize, the model generates a recession as well as a crash in the stock market.</p> <p>In the second chapter, I explore the extent to which expectations about innovations in the financial sector may have contributed to both the boom and bust associated with the ``Great Recession''. Making a connection between the ``boom-years'' of easy credit and the crises of 2008, I argue that agents' overly-optimistic expectations of the benefits associated with financial innovation led to a flood of liquidity in the financial sector, lowering interest rate spreads and facilitating the boom in asset prices and economic activity. When the events of 2007-2009 led to a re-evaluation of the effectiveness of these new products, agents revised their expectations regarding the actual efficiency gains available to the financial sector and this led to a withdrawal of liquidity from the financial system, a reversal in credit spreads and asset prices and a bust in real activity. Following the news-shock approach, I model the boom and bust cycle in terms of an expected future fall in the costs of bankruptcy which are eventually not realized. The build up in liquidity and economic activity in expectation of these efficiency gains is then abruptly reversed when agents' hopes are dashed. The model generates counter-cyclical movement in the spread between lending rates and the risk-free rate which is driven purely by expectations, even in the absence of any exogenous movement in bankruptcy costs as well as an endogenous rise and fall in asset prices and leverage.</p> <p>In the final chapter, I explore the extent to which a ``bout of optimism'' during a period of technological change such as the 1990's could produce not just a boom in consumption, investment and hours-worked, but also rapid growth in productivity itself. I present a theoretical model where the economy endogenously adopts the technological ideas of a slowly evolving technological frontier, and show that the presence of a ``technological gap'' between unadopted ideas and current productivity can lead to multiple equilibria and therefore the possibility that changes in beliefs can be self-fulfilling, often referred to as sunspots. In the model these sunspots take the form of beliefs about the value of adopting the new technological ideas, and unleash both a boom in aggregate quantities as well as eventual productivity growth, increasing the value of adoption and self-confirming the beliefs. In this sense, the model provides an alternative interpretation of the empirical news-based results that identify expectational booms that precede growth in TFP. Finally, I demonstrate that the scope for the indeterminacies is a function of the steady-state growth rate of the underlying frontier of technological ideas, and that during times of low growth in ideas or technological stagnation, the potential for indeterminacies and thus belief-driven productivity growth diminishes.</p> / Doctor of Philosophy (PhD)

Notre thèse consiste à expliquer, en apportant quelques éléments théoriques, les imperfections des stress tests macro-prudentiels d’EBA/BCE, et de proposer une nouvelle méthodologie de leur application ainsi que deux stress tests spécifiques en complément. Nous montrons que les stress tests macro-prudentiels peuvent être non pertinents lorsque les deux hypothèses fondamentales du modèle de base de Gordy-Vasicek utilisé pour évaluer le capital réglementaire des banques en méthodes internes (IRB) dans le cadre du risque de crédit (portefeuille de crédit asymptotiquement granulaire et présence d’une seule source de risque systématique qui est la conjoncture macro-économique), ne sont pas respectées. Premièrement, ils existent des portefeuilles concentrés pour lesquels les macro-stress tests ne sont pas suffisants pour mesurer les pertes potentielles, voire inefficaces si ces portefeuilles impliquent des contreparties non cycliques. Deuxièmement, le risque systématique peut provenir de plusieurs sources ; le modèle actuel à un facteur empêche la répercussion propre des chocs « macro ».Nous proposons un stress test spécifique de crédit qui permet d’appréhender le risque spécifique de crédit d’un portefeuille concentré, et un stress test spécifique de liquidité qui permet de mesurer l’impact des chocs spécifiques de liquidité sur la solvabilité de la banque. Nous proposons aussi une généralisation multifactorielle de la fonction d’évaluation du capital réglementaire en IRB, qui permet d’appliquer les chocs des macro-stress tests sur chaque portefeuille sectoriel, en stressant de façon claire, précise et transparente les facteurs de risque systématique l’impactant. Cette méthodologie permet une répercussion propre de ces chocs sur la probabilité de défaut conditionnelle des contreparties de ces portefeuilles et donc une meilleure évaluation de la charge en capital de la banque. / Our thesis consists in explaining, by bringing some theoretical elements, the imperfections of EBA / BCE macro-prudential stress tests, and proposing a new methodology of their application as well as two specific stress tests in addition. We show that macro-prudential stress tests may be irrelevant when the two basic assumptions of the Gordy-Vasicek core model used to assess banks regulatory capital in internal methods (IRB) in the context of credit risk (asymptotically granular credit portfolio and presence of a single source of systematic risk which is the macroeconomic conjuncture), are not respected. Firstly, they exist concentrated portfolios for which macro-stress tests are not sufficient to measure potential losses or even ineffective in the case where these portfolios involve non-cyclical counterparties. Secondly, systematic risk can come from several sources; the actual one-factor model doesn’t allow a proper repercussion of the “macro” shocks. We propose a specific credit stress test which makes possible to apprehend the specific credit risk of a concentrated portfolio, as well as a specific liquidity stress test which makes possible to measure the impact of liquidity shocks on the bank’s solvency. We also propose a multifactorial generalization of the regulatory capital valuation model in IRB, which allows applying macro-stress tests shocks on each sectorial portfolio, stressing in a clear, precise and transparent way the systematic risk factors impacting it. This methodology allows a proper impact of these shocks on the conditional probability of default of the counterparties of these portfolios and therefore a better evaluation of the capital charge of the bank.