Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America.
PLoS One. 2010 Nov 10;5(11):e13541. doi: 10.1371/journal.pone.0013541.
With urban population increasing dramatically worldwide, cities are playing an increasingly critical role in human societies and the sustainability of the planet. An obstacle to effective policy is the lack of meaningful urban metrics based on a quantitative understanding of cities. Typically, linear per capita indicators are used to characterize and rank cities. However, these implicitly ignore the fundamental role of nonlinear agglomeration integral to the life history of cities. As such, per capita indicators conflate general nonlinear effects, common to all cities, with local dynamics, specific to each city, failing to provide direct measures of the impact of local events and policy. Agglomeration nonlinearities are explicitly manifested by the superlinear power law scaling of most urban socioeconomic indicators with population size, all with similar exponents (1.15). As a result larger cities are disproportionally the centers of innovation, wealth and crime, all to approximately the same degree. We use these general urban laws to develop new urban metrics that disentangle dynamics at different scales and provide true measures of local urban performance. New rankings of cities and a novel and simpler perspective on urban systems emerge. We find that local urban dynamics display long-term memory, so cities under or outperforming their size expectation maintain such (dis)advantage for decades. Spatiotemporal correlation analyses reveal a novel functional taxonomy of U.S. metropolitan areas that is generally not organized geographically but based instead on common local economic models, innovation strategies and patterns of crime.
随着世界城市人口的急剧增长,城市在人类社会和地球可持续性方面发挥着越来越重要的作用。有效政策的一个障碍是缺乏基于对城市的定量理解的有意义的城市指标。通常,线性人均指标用于描述和对城市进行排名。然而,这些指标隐含地忽略了非线性集聚的基本作用,而这种集聚是城市发展历史的核心。因此,人均指标将所有城市共有的一般非线性效应与每个城市特有的局部动态混为一谈,无法提供对局部事件和政策影响的直接衡量。集聚的非线性通过大多数城市社会经济指标与人口规模的超线性幂律标度明确体现出来,所有这些指标都具有相似的指数(1.15)。因此,较大的城市不成比例地成为创新、财富和犯罪的中心,其程度大致相同。我们利用这些普遍的城市规律来开发新的城市指标,以分解不同尺度的动态,并提供对当地城市绩效的真实衡量。新的城市排名和对城市系统的新颖而简单的视角出现了。我们发现,当地城市动态具有长期记忆,因此表现低于或高于其规模预期的城市会保持这种(劣势)优势几十年。时空相关分析揭示了美国大都市地区的一种新的功能分类法,这种分类法通常不是基于地理组织,而是基于共同的当地经济模型、创新战略和犯罪模式。