Scaling of Atypical Knowledge Combinations in American Metropolitan Areas from 1836 to 2010
研究了174年间美国大都市区发明中非典型知识组合与人口规模的超线性缩放关系，发现大城市不仅发明数量多，质量也更高。
Cities are epicenters for invention. Scaling analyses have verified the productivity of cities and demonstrate a superlinear relationship between cities’ population size and invention performance. However, little is known about what kinds of inventions correlate with city size. Is the productivity of cities only limited to invention quantity? I shift the focus on the quality of idea creation by investigating how cities influence the art of knowledge combinations. Atypical combinations introduce novel and unexpected linkages between knowledge domains. They express creativity in inventions and are particularly important for technological breakthroughs. My study of 174 years of invention history in metropolitan areas in the US reveals a superlinear scaling of atypical combinations with population size. The observed scaling grows over time indicating a geographic shift toward cities since the early twentieth century. The productivity of large cities is thus not only restricted to quantity but also includes quality in invention processes.