Using original, representative survey data, we document that analytical, routine, and manual job tasks can be measured with high validity, vary substantially within and between occupations, are significantly related to workers' characteristics, and are robustly predictive of wage differences between occupations and among workers in the same occupation. We offer a conceptual framework that makes explicit the causal links between human capital endowments, occupational assignment, job tasks, and wages, which motivate a Roy model of the allocation of workers to occupations. We offer two simple tests of the model's gross predictions for the relationship between tasks and wages, both of which receive qualified empirical support.

We offer a unified analysis of the growth of low-skill service occupations between 1980 and 2005 and the concurrent polarization of US employment and wages. We hypothesize that polarization stems from the interaction between consumer preferences, which favor variety over specialization, and the falling cost of automating routine, codifiable job tasks. Applying a spatial equilibrium model, we corroborate four implications of this hypothesis. Local labor markets that specialized in routine tasks differentially adopted information technology, reallocated low-skill labor into service occupations (employment polarization), experienced earnings growth at the tails of the distribution (wage polarization), and received inflows of skilled labor. (JEL J24, J31, R23)

We analyze the effect of rising Chinese import competition between 1990 and 2007 on US local labor markets, exploiting cross-market variation in import exposure stemming from initial differences in industry specialization and instrumenting for US imports using changes in Chinese imports by other high-income countries. Rising imports cause higher unemployment, lower labor force participation, and reduced wages in local labor markets that house import-competing manufacturing industries. In our main specification, import competition explains one-quarter of the contemporaneous aggregate decline in US manufacturing employment. Transfer benefits payments for unemployment, disability, retirement, and healthcare also rise sharply in more trade-exposed labor markets. (JEL E24, F14, F16, J23, J31, L60, O47, R12, R23)

This paper explores the geographic overlap of trade and technology shocks across local labor markets in the United States. Regional exposure to technological change, as measured by specialization in routine task-intensive production and clerical occupations, is largely uncorrelated with regional exposure to trade competition from China. While the impacts of technology are dispersed throughout the United States, the impacts of trade tend to be more geographically concentrated, owing in part to the spatial agglomeration of labor-intensive manufacturing. Our findings highlight the feasibility of separately identifying the impacts of recent changes in trade and technology on US regional economies.