Heterogeneity and Wage Inequalities over the Life Cycle

Using panel data from a single cohort of French male wage earners observed over a long span of 30 years starting at their entry in the labor market, we estimate parameters of a human capital investment model by random and fixed effect methods. Individual wage proles are described by their individual-specific level, slope and curvature. This allows a fine decomposition of the variance of (log-)wages at different times of the life-cycle and in the long run. Among salient results, short run time-varying inequalities are shown to be larger that long run inequality by a factor of 20% to 80%. Individual permanent heterogeneity explain between 60 to 90% of the variance of wages. Single dimensional heterogeneity explains well those variances at a point in time but not over the whole period or in the long run. Multidimensional heterogeneity is needed and in particular under the form of a horizon individual effect.