Productivity in cities: self-selection and sorting
研究了城市生产率高的原因，发现城市环境通过自我选择机制吸引高能力工人，从而提升匹配质量，最终提高所有工人的生产率。
Productivity is high in cities partly because the urban environment acts as a self-selection mechanism. If workers have imperfect information about the quality of workers with whom they match and matches take place within cities, then high-ability workers will choose to live and work in expensive cities. This self-selection improves the quality of matches in such cities. The mechanism may be reinforced by the development of informational networks in cities with a large proportion of high-ability workers. As a consequence productivity in these cities is high for workers of all ability types.