Interactions between heterogeneity and uninsurable individual fluctuations: applications to wealth inequality and unemployment risk.

Summary This thesis is devoted to the study of heterogeneity as a result of individual income fluctuations. We apply the methodology of heterogeneous agent models to explore this link from two perspectives. First, we focus on the study of the determinants of wealth distribution. We build a detailed model of the French economy by distinguishing seven socio-professional categories, and by integrating inheritance. The gradual construction of a model that faithfully reproduces the distribution of wealth then requires taking into account a bequest motive, as well as the existence of differentials in savings returns. We evaluate the impact of inheritance on the concentration of wealth, and find that inheritance slightly increases inequality, but mostly affecting the middle classes, and little the upper wealth fractiles. The degree of intergenerational mobility in terms of income is sufficiently high that inheritance allows low-income agents to enter the middle classes. Second, we isolate the risk of unemployment and construct a job search model with precautionary savings. We then determine the optimal long-run compensation profile, which is found to be regressive and lower than its current level. We then study the feasibility of moving to the long-run optimum from normative and positive perspectives. In normative terms, it appears that it is not desirable to lower the allocation to its long-run optimum, because the transition is costly for agents. They must increase their precautionary savings, and thus reduce their consumption on the transitional path. In positive terms, we study the political-economic equilibrium, and show that for plausible voting frequencies, the equilibrium compensation is higher than the optimum.