Accounting for Changes in Between-Group Inequality

We provide an assignment model to decompose changes in between-group wage inequality into changes in the composition of the workforce, the productivity/demand for tasks, computerization, and labor productivity. The model incorporates comparative advantage between many groups of workers, many types of equipment, and many tasks and yet may be parameterized and estimated in a transparent manner. Our identification of parameters, measurement of shocks, and the equilibrium equation determining wages are all very similar to what have been used in previous reduced-form analyses. We use U.S. data on the allocation of workers to occupations and computer usage as well as changes in average wages across worker groups between 1984 and 2003 to parameterize our model. We find that computerization and changes in task productivity/demand, which are both measured without directly using data on changes in wages, jointly explain the majority of the rise in the skill premium and more disaggregated measures of between-eduation group inequality as well as roughly half of the rise in the relative wage of women over this time period. We show how to link the strength of these two forces to changes in the extent of international trade.