Spatial Polarisation*
研究了1980-2008年美国大城市就业极化现象，发现技能偏向型技术进步是主因，高技能工人对低技能服务的需求加剧了空间极化。
Abstract We document the emergence of spatial polarisation in the United States during the 1980–2008 period. This phenomenon is characterised by stronger employment polarisation in larger cities, both at the occupational and the worker levels. We quantitatively evaluate the role of technology in generating these patterns by constructing and calibrating a spatial equilibrium model. We find that faster skill-biased technological change in larger cities can account for a substantial fraction of spatial polarisation in the United States. Counterfactual exercises suggest that the differential increase in the share of low-skilled workers across city size is due mainly to the large demand by high-skilled workers for low-skilled services and, to a smaller extent, to the higher complementarity between low- and high-skilled workers in production relative to middle-skilled workers.