Since the end of October 2010, the Bank of Japan has been pursuing a new Asset Purchase Programme, which includes, among other things, direct intervention in the domestic stock market through the purchase of exchange-traded funds. This research study evaluated the impact of the Bank of Japan’s exchange-traded fund purchase programme on market returns using an event study methodology. An investigation into a sample of 33 intervention events in the Nikkei 400 exchangetraded fund and 303 intervention events in the Nikkei 225 exchange-traded fund, found that the average abnormal one-day return is -1.36% for the Nikkei 400 exchange-traded fund and -1.39% for the Nikkei 225 exchange-traded fund, while the average abnormal five-day return is -0.63% and -1.11% for each exchange-traded fund respectively. Due to the high volatility, statistically the returns are indistinguishable from zero. However, this study presents evidence that the Bank of Japan intervenes predominantly during large decreases in the market. Hence, there is suggestive evidence that the Bank of Japan’s policy is effective at reducing market losses, but is not extensive enough to significantly increase returns.

The master thesis focuses on the economical development of Europe after the fi-nancial crisis and the steps used by the ECB needed for the recovery of the Europe-an economy. The empirical part analyzes the quantitative easing of the ECB and its delayed impact on inflation. The second part of the empirical master thesis re-searches the quantitative easing of the ECB and its impact on the rentability of commercial banks in the Eurozone (Deutsche Bank, BNP Paribas) and identifies factors with the strongest impact on the chosen commercial banks as well. The rentability analysis of commercial banks and the impact on inflation is made by a regression time-series analysis.

Les trois chapitres de cette thèse ont pour objectif de contribuer à une meilleure compréhension de la manière dont les politiques non-conventionnelles affectent les prix d’actifs. Ils revisitent également de manière empirique la question de l’impact de l’offre sur les prix d’actifs, et plus généralement des limites imposées à l’arbitrage, des frictions dans la réallocation des portefeuilles. Chaque chapitre présente de nouvelles données permettant de quantifier les mécanismes à l’œuvre dans le cas du programme d’achat d’actifs de l’Eurosystème (APP). Le chapitre 1 propose un modèle de portefeuille simple permettant de penser les mesures non conventionnelles dans un cadre cohérent. Les exercices empiriques confirment l’existence de plusieurs canaux de transmission des prix et évaluent l’impact de l’APP. Le chapitre 2 jette un nouvel éclairage sur le canal du rééquilibrage de portefeuille. Les fortes frictions liées à la réallocation, la forte demande d’“habitat préféré” et le faible niveau de substituabilité entre actifs permettent d’avoir un impact sur les prix, tout en limitant possiblement les retombées sur l’économie. Le chapitre 3 suggère que l’effet des achats de titres passe également si ce n’est en premier lieu par l’augmentation du coût d’emprunt de ces titres, ce qui a des répercussions sur la dispersion des taux du marché monétaire à court terme et pourrait rendre difficile à l’avenir la transmission de la politique monétaire conventionnelle si les taux autrefois considérés comme sans risque et contrôlables par la banque centrale ne pouvaient pas être contrôlés aussi précisément qu’auparavant. / The three chapters contained in this PhD thesis aim at contributing to a better understanding of how unconventional monetary policies and in particular asset purchases affect asset prices. As such, they also revisit the question of the impact of bond supply on bond prices, and more broadly the questions of limits to arbitrage, frictions in portfolio reallocation and the role of intermediaries. Each chapter brings new original data to quantify the effect on bond prices, on the short term rates, and on the portfolio reallocation of investors. Chapter 1 built a simple portfolio model allows to think of them in a consistent framework, and suggests that the type of asset purchased, the degree of risk aversion or how assets covary are important. The empirical exercises confirm the existence of several transmission channels to prices and assess the impact of the European APP. Chapter 2 sheds a new light on portfolio rebalancing in terms of asset classes and shows it is more limited than previously thought. Heavy frictions to reallocation, strong “preferred habitat” demand and low level of substituability between assets allow for price impact of central bank asset purchases but at the same time possibly limit the spillovers on the economy. The main channel through which APP affects price might be even be more indirect that one thought: chapter 3 suggests that it might come from reducing asset supply and increasing the cost of borrowing them. This has repercussions on the dispersion of short term money market rates and might be challenging in the future if rates once considered as risk free and controllable by the central bank cannot be controlled as precisely as before. In other terms, controlling the long end of the yield curve might in part comes at the cost of loosing part of the control on the short end.