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

Abstract

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.

Keywords

Urban scaling

Population mobility

Urban economic outputs

Social interactions

Agglomeration effects

1. Introduction

Cities are concentrations not only of population but rather of socio-economic interactions (Jacobs, 1969). As one of the cornerstones to explore the new science of cities (Rybski, Arcaute, amp; Batty, 2018), urban scaling shows how urban attributes vary with size and the relationship between them (Batty, 2013b; West, 2017). Numerous urban indicators referring to material resource or measure of social activity, Y(t), scale with urban size N(t) across cities, obeying the power law form Y(t) = Y0N(t)beta;, where Y0 is a normalized constant and beta; is the scaling exponent (L. M. Bettencourt, Lobo, Helbing, Kuhnert, amp; West, 2007). This paradigm emphasizes the basic function of urban population size in the growth of socio-economic activities and infrastructure (Joseacute; Lobo, Bettencourt, Strumsky, amp; West, 2013). It also expresses that urban economic outputs brought by urban population size is nonlinear, which also determines the agglomeration effects or economies of scale characteristics of urban indicators in the process of urban development (L. M. Bettencourt, Lobo, Strumsky, amp; West, 2010; Florida, 2005). Socio-economic related properties of a city grow faster than population, called super-linear scaling regimes, characterized by a scaling exponent greater than one, while infrastructure presents sub-linear scaling regimes because of economies of scale (L. M. Bettencourt et al., 2007).