Task Specialization in U.S. Cities from 1880 to 2000
利用1880-2000年美国微观数据，通过分析职业描述中的动词，发现大都市区互动性职业的就业份额增长更快，表明交通和通信成本下降促使城市按互动任务比较优势专业化。
Abstract We develop a new methodology for quantifying the tasks undertaken within occupations using over 3,000 verbs from more than 12,000 occupational descriptions in the Dictionary of Occupational Titles (DOTs). Using micro data from the United States from 1880 to 2000, we find an increase in the employment share of interactive occupations within sectors over time that is larger in metro areas than nonmetro areas. We interpret these findings using a model in which reductions in transport and communication costs induce urban areas to specialize according to their comparative advantage in interactive tasks. We present suggestive evidence relating increases in employment in interactive occupations to improvements in transport and communication technologies. Our findings highlight a change in the nature of agglomeration over time toward an increased emphasis on human interaction.