Worker heterogeneity and labor market frictions.

Summary This thesis is composed of various works in macroeconomics and labor economics. These works revolve around the same theme: the study of labor markets whose functioning is hampered by information frictions and in which workers differ from one another in their characteristics. These two elements are essential to our understanding of the labor market and their consideration makes it possible to better understand empirical than normative issues. The first chapter of this thesis is on the side of empirical questioning. It shows that the combination of information frictions and heterogeneity of individual skills can explain a significant part of the fluctuations observed in the flows of workers entering and leaving the labor force. The second chapter also takes a positive approach while considering government intervention as one of the mechanisms for allocating resources in the labor market. It examines how certain public policies interact with individual job-seeking and human capital investment decisions, and may have contributed in the long run to Europe's poorer performance relative to the United States in the employment of older workers. The third chapter lends itself more to a normative reading. It proposes a quantitative analysis of the effects of redundancy payments on employment and individual well-being. To do this, it places itself in a framework where the incompleteness of insurance markets leads workers to accumulate precautionary savings.