La thèse examine l'optimalité de la Zone Euro une vingtaine d'années après le débat entre la Commission Européenne puis Frankel et Rose (1998) et Krugman (1993). Elle porte principalement sur les membres fondateurs (1980-2010), et s'intéresse secondairement à l'élargissement de la zone monétaire aux PECO. Elle retient un critère transversal d'analyse: la convergence des cycles économiques des pays membres évoqué dès Mundell (1961). L'analyse de la convergence des cycles (corrélation) et des chocs (modèle SVAR) est complétée par celle des déterminants de la première faite à l'aide de modèles à équations simultanées et de modèles dynamiques sur données de panel, ceci afin de répondre à la question de l'endogénéité des critères d'optimalité et ses conditions de réalisation. Enfin, le cas des biens non échangeables mérite d'être étudié à la lumière des caractéristiques de la crise économique de 2007-2008 qui a fortement touché les pays membres en rattrapage. L'analyse de la synchronisation des cycles immobiliers tient compte des caractéristiques particulières du secteur immobilier. La zone montre des divergences qui s'accentuent à nouveau avec la crise actuelle qui met en cause la viabilité de la monnaie unique ainsi que l'optimalité de la zone monétaire. / We examine the optimality of the euro zone two decades after the debate between the European Commission and Frankel and Rose (1998) versus Krugman (1993). The study focuses on the founding members between 1980 and 2010, and it also deals with the expansion of the currency area to CEECs. We retain a main convergence criterion through the analysis: the convergence of business cycles in member countries [Mundell (1961)]. The analysis of the convergence of cycles (with their bilateral correlations) and shocks at their origin (using a SVAR model) is completed by the study of its determinants (using simultaneous equations models and dynamic panel models). We then address the issue of endogeneity of the optimality criteria and its conditions of realization. Finally, the case of the real estate sector deserves to be studied in light of the characteristics of the economic crisis of 2007 - 2008 which has greatly affected catching up members. The analysis of the housing cycles takes also into account the specific characteristics of the housing sector. The area displays differences that are growing again with the crisis and calls upon the viability of the Euro Zone and the optimal currency area.

This thesis, motivated by my reflections about the failings of monetary policy implementation as a cause of the sub-prime crisis, attempts to answer the following inquiries: (i) whether interest rates have played a major role in generating the house price fluctuations in the U.S., (ii) what are the effects of accommodative monetary policy on the economy given banks' excessive risk-taking, and (iii) whether an optimal monetary policy rule can be found for curbing credit-driven economic volatilities in the model economy with unconventional transmission channels operating. By using a decomposition technique and regression analysis, it can be shown that short-term interest rates exert the most potent influence on the evolution of the volatile components of housing prices. One possible explanation for this is that low policy rates for a prolonged period tend to encourage bankers to take on more risk in lending. This transmission channel, labelled as the risk-taking channel, accounts for the gap to some extent between the forecast and the actual impact of monetary policy on the housing market and the overall economy. A looser monetary policy stance can also shift the preference of economic agents toward housing as theoretically and empirically corroborated in the context of choice between durable and nondurable goods. This transmission route is termed the preference channel. If these two channels are operative in the economy, policy makers need to react aggressively to rapid credit growth in order to stabilize the paths of housing prices and output. These findings provide meaningful implications for monetary policy implementation. First of all, central bankers should strive to identify in a timely fashion newly emerging and state-dependent transmission channels of monetary policy, and accurately assess the impact of policy decisions transmitted through these channels. Secondly, the intervention of central banks in the credit or housing market by adjusting policy rates can be optimal, relative to inaction, in circumstances where banks' risk-taking and the preference for housing are overly exuberant.