Thesis: This thesis brings together different evaluations of recent reforms of the French pension system using two complementaryapproaches: ex post evaluation using microeconometrics techniques and ex ante evaluation built on microsimulationmodelling.The first part of the thesis is based on microestimations using administrative data of the French Social Security agency (Cnav). We first use changes in the rules of mandatory retirement to identify an effect of labordemand on retirement behavior. In a second contribution we estimate the effect of the increase in the early retirement age implemented by the 2010 reform. Besides its effect over employment, we study thepotential substitution effects of the reform towards alternative schemes like unemployment insurance.The second part of the thesis focuses on evaluation by microsimulation. A first study evaluates the effect of the increase in therequired insurance duration implemented by the 2003 reform. The principle of the reform – preserving a constant ratio between work and retirement duration – is discussed on theoretical grounds, and then confronted with the long-term evolutions projected by the Insee Destinie model. Finally, we use the Pensipp model of the Institute of public policies to simulate the effect of originalreforms reducing the growth dependence of the pension system and the uncertainty over financial balance it generates.