Scaling of urban economic outputs: insights both from urban population size and population mobility

摘要

Urban scaling laws assume that the performance of a city largely relies on its urban population size. However, two cities with the same population size may have vastly different economic outputs, which reveals that factors apart from urban size (a measurement of intra-urban interactions) determine their economic outputs. Economic production is essentially the product of social interactions. Urban population size and interurban interactions reflected by population mobility were both considered to evaluate the scaling of urban economic outputs in this paper. We quantified the scaling relationship between urban economic outputs and interurban interactions, and compared it with the paradigm derived from urban size. Results showed that urban economic outputs scale with urban interactions across cities and present the same super-linear scaling regimes but with a greater scaling exponent. A deeper looking showed that interurban interactions definitely bring a more obvious super-linearity than population size but the scaling relationship between urban size and economic outputs is more robust. Urban population size has a greater impact on Gross Domestic Product (GDP), secondary and tertiary industries output products, total retail sales of consumer goods and total wage with 60- 65% relative contribution. For exports, interurban interactions and urban population size are almost equally important. We also proved that interactions between cities are significantly positively correlated with urban extra growth. These findings provide convictive evidence that in addition to population size, interurban interaction is also crucial for exploring the scaling of urban growth. Our results are enlightening to the study of mechanisms and evolutions of urban scaling that interurban interaction besides urban population size should both be a vital consideration to urban economic outputs.