Sources of earnings inequality : Estimates from an on-the-job search model of the U.S. labor market

Since the early 1980s the labor market in the United States has seen a substantial increase in earnings dispersion. We study the issue by developing an on-the-job search model of the US labor market that allows for wage and employment mobility as a result of optimal individual behavior. We estimate its structural parameters on PSID data at different points in time to clarify the sources of the evolution of earnings inequality and instability between 1987 and 1996. This procedure allows to: compute lifetime measure of inequality on top of the usual cross-sectional measure of inequality and provide counterfactual experiments that evaluate the contribution of different parameters to changes over time by taking into account some equilibrium effects. We find that the increase in lifetime inequality and in cross-sectional inequality have been generated by different sources and that these sources are different by skills: changes in the wage offer distribution are the main determinant of the increase in inequality for skilled workers while both mobility changes and wage offer distribution changes are needed to explain changes for the unskilled.