Stress Tests et Risques financiers

This thesis has set a comprehensive framework to assess the relevance of financial stress tests, identifying their main drawbacks. Three robust and flexible model frameworks have been proposed to improve current practices in each of the tests’ stages. This is achieved through: (i) a semi-parametric EVT–Pair-copulas model for financial risk factors, with a specific focus on extreme values, (ii) a valuation model to assess the impact of risk factors on a financial system, through direct and indirect effects, contagion channels, and considering private and public response functions, and (iii) a Bayesian-based approach to run a systematic selection of stress scenarios for nonlinear portfolios. The presented risk model has proven to outperform commonly used specifications, hence increasing the test’s credibility. Estimated for the French banking system, the valuation model revealed the related risk profile and the main vulnerabilities. Public responses turned to be of vital interest. Finally, the Bayesian approach allows replacing the traditional subjective scenarios and including the tests’ results in quantitative risk management alongside with other conventional toolsCette thèse établit un cadre d’évaluation des stress tests financiers, en identifiant leurs principales limites. Trois approches ont été proposées pour améliorer les pratiques actuelles à chaque étape du processus. Elles incluent : (i) un modèle semi-paramétrique TVE–copules-paires pour les facteurs de risque financiers, avec un accent particulier sur les valeurs extrêmes, (ii) un modèle d'évaluation pour estimer l'impact de ces facteurs sur un système financier, via des effets directs, indirects et de contagion, en considérant les réactions endogènes publiques et privées, et (iii) une approche bayésienne pour mener une sélection systématique des scénarios de stress pour des portefeuilles non linéaires. Le modèle de risque a montré de meilleures performances par rapport à la plupart des spécifications courantes ; ce qui augmente la crédibilité du test. Le modèle d'évaluation est estimé pour le système bancaire français, révélant ses principales sources de vulnérabilité et le rôle clé des réactions publiques. Enfin, l'approche bayésienne a permis de remplacer les scénarios subjectifs traditionnels et d’inclure les résultats de stress tests dans la gestion quantitative des risques aux côtés des autres outils conventionnel

Does Monetary Policy Respond to Commodity Price Shocks?

International audienceCommodity prices, especially oil prices, peaked in the aftermath of the financial crisis of 2007 and they have remained highly volatile. All things being equal, the increase in commodity prices may induce a similar tendency of inflation and hence become a monetary policy issue. However, the impact of the changes of commodity prices on inflation is not clear. In this paper, by using Markov-switching models we show that there is an implicit impact of commodity markets on short-term interest rates for a set of heterogeneous countries (the U.S., the Euro area, Brazil, India, Russia and South Africa) over the period from January 1999 to August 2012. Besides, the VAR models reveal that short-term interest rates respond to commodity volatility shocks whatever the country. Moreover, the linkage between commodity markets and monetary policy instruments is stronger since the recent financial crisis

On the determinants of food price volatility

International audienceIn this paper, we investigate the determinants of price volatility for six major food commodities fromJanuary 2001 to March 2013. In the recent literature, real economic activity, biofuel production, oilprices and financial markets indicators are commonly considered to be the main drivers of pricevolatility. We identify and analyse the relationships between these macroeconomic and financialfactors and our commodities within a Bayesian multivariate framework. Then we assess the effect ofeach factor on food volatility in the recent period. We show that, although results depend on foodcommodities, they are consistent with those available in the latest studies. In other words, the twomost recent surges in food prices do not significantly change the dynamics of these prices. We havealso performed an analysis of the effects of certain shocks on food commodity markets. Theseexercises do not reveal the existence of coherent groups of food commodities