THE SKILL COMPOSITION OF U.S. CITIES*
研究了美国大都市区高技能劳动者比例差异的原因，发现行业中性生产率差异和商业服务部门规模是关键因素，并提出了一个投入共享模型来解释这些现象。
This article explores why the fraction of highly educated workers varies across U.S. metropolitan areas. It documents a set of facts that pose challenges for a number of theories. Notably, (i) cities are characterized by industry neutral differences in skilled labor productivity and (ii) the size of the business services sector is strongly correlated with cities' skill compositions. Motivated by these observations, I propose an input sharing model, in which nontraded business services complement skilled labor. I show that the model accounts for all of the empirical regularities documented in the article.