Capital accumulation, wealth heterogeneity and employment flows.

Summary This thesis proposes an integrative approach to capital accumulation behavior and job search decisions in order to account for transitions in the labor market and more generally for contemporary fluctuations in unemployment. This integrative perspective draws its legitimacy from the close links between the traditional literature on job search models initiated by Phelps and a reflection on the market for capital, such as the questions of the sources of financing for research, the discount rate of its return and the adjustments to employment that give this factor a temporality similar to that of capital. We show in return that the recognition of these links is essential in both the positive and normative analysis of employment flows. From the point of view of firms, the introduction of endogenous adjustments of capital and interest rates, within the framework of stochastic matching models à la Mortensen and Pissarides, is able to account for the strong persistence observed in unemployment and job destruction rates. From this perspective, the introduction of employment protection can stabilize the economy and increase the welfare of risk-averse workers. From the point of view of risk averse workers, we show from micro-econometric estimates on the European Panel that their job search is strongly influenced by their wealth. We then reassess the welfare gains of unemployment benefits when we take into account the possibility for workers to self-insure by saving in a framework of incomplete markets. We show that saving is a poor substitute for benefits when we take into account variations in the interest rate and the duration of unemployment episodes over the business cycle.