Crises, financial frictions and macroeconomic modeling.

Summary The interaction between the financial and real spheres has long been neglected in macroeconomic models, which generally assume that the former is neutral. The recent subprime crisis demonstrates that this is not the case. This thesis proposes three essays on the role of the financial sector, and more particularly the banking sector, in the light of the latest crisis. The first is to give a formal framework to the exceptional nature of the crisis by abandoning the assumption of normality of 'residual events'. Our results refute the 'normal' character of the crisis but, more importantly, highlight the biases in terms of economic diagnoses to consider it as such.Furthermore, one of the exceptional effects of this crisis was the use of unconventional monetary policies. The second part of the thesis suggests that uncertainty in the interbank markets is a probable reason for the ineffectiveness of conventional monetary policies. The third part of the thesis proposes a study of the impact of the new Basel III regulations on the real sector. The lack of positive externalities between the implementation of the capitalization constraint and the LCR further accentuates the output gap between SMEs and large firms, leading to an even more significant overall recessionary impact. A slower and perfectly announced implementation of the new regulatory standards could nevertheless mitigate these effects.