The nested structure of urban business clusters

Although the cluster theory literature is bountiful in economics and regional science, there is still a lack of understanding of how the geographical scales of analysis (neighbourhood, city, region) relate to one another and impact the observed phenomenon, and to which extent the clusters are industrially bound or geographically consistent. In this paper, we cluster spatial economic activities through a multi-scalar approach following percolation theory. We consider both the industrial similarity and the geographical proximity of firms, through their joint probability function which is constructed as a copula. This gives rise to an emergent nested hierarchy of geoindustrial clusters, which enables us to analyse the relationships between the different scales, and specific industrial sectors. Using longitudinal business microdata from the Office for National Statistics, we look at the evolution of clusters which spans from very local groups of businesses to the metropolitan level, in 2007 and in 2014, so that the changes stemming from the financial crisis can be observed.Comment: 20 pages, 10 figure

Paradoxical Interpretations of Urban Scaling Laws

Scaling laws are powerful summaries of the variations of urban attributes with city size. However, the validity of their universal meaning for cities is hampered by the observation that different scaling regimes can be encountered for the same territory, time and attribute, depending on the criteria used to delineate cities. The aim of this paper is to present new insights concerning this variation, coupled with a sensitivity analysis of urban scaling in France, for several socio-economic and infrastructural attributes from data collected exhaustively at the local level. The sensitivity analysis considers different aggregations of local units for which data are given by the Population Census. We produce a large variety of definitions of cities (approximatively 5000) by aggregating local Census units corresponding to the systematic combination of three definitional criteria: density, commuting flows and population cutoffs. We then measure the magnitude of scaling estimations and their sensitivity to city definitions for several urban indicators, showing for example that simple population cutoffs impact dramatically on the results obtained for a given system and attribute. Variations are interpreted with respect to the meaning of the attributes (socio-economic descriptors as well as infrastructure) and the urban definitions used (understood as the combination of the three criteria). Because of the Modifiable Areal Unit Problem and of the heterogeneous morphologies and social landscapes in the cities internal space, scaling estimations are subject to large variations, distorting many of the conclusions on which generative models are based. We conclude that examining scaling variations might be an opportunity to understand better the inner composition of cities with regard to their size, i.e. to link the scales of the city-system with the system of cities

A modular modelling framework for hypotheses testing in the simulation of urbanisation

In this paper, we present a modelling experiment developed to study systems of cities and processes of urbanisation in large territories over long time spans. Building on geographical theories of urban evolution, we rely on agent-based models to 1/ formalise complementary and alternative hypotheses of urbanisation and 2/ explore their ability to simulate observed patterns in a virtual laboratory. The paper is therefore divided into two sections : an overview of the mechanisms implemented to represent competing hypotheses used to simulate urban evolution; and an evaluation of the resulting model structures in their ability to simulate - efficiently and parsimoniously - a system of cities (the Former Soviet Union) over several periods of time (before and after the crash of the USSR). We do so using a modular framework of model-building and evolutionary algorithms for the calibration of several model structures. This project aims at tackling equifinality in systems dynamics by confronting different mechanisms with similar evaluation criteria. It enables the identification of the best-performing models with respect to the chosen criteria by scanning automatically the parameter along with the space of model structures (as combinations of modelled dynamics).Comment: 21 pages, 3 figures, working pape

What is emerging? Understanding urbanisation dynamics in BRICS countries through a geographical approach, the case of Russia and South Africa

International audienc

Decentralisation versus Territorial Inequality: A Comparative Review of English City Region Policy Discourse

The most recent English attempts at decentralisation take the shape of the city region devolution policy agenda. Decentralisation claims to empower localities and address regional growth imbalances, while creating a variety of new temporary and selective fiscal and geographic arrangements in policy-making that have the potential to create the opposite effect. This paper focuses on the relationship between decentralisation and territorial inequalities through the analysis of strategic discourse of six ‘devolved authorities’. A quantitative, qualitative, and comparative approach to this question complements the traditional insights obtained from in-depth case study analysis using actors’ interviews. It focuses on city regions’ official discourse of self-conceptualisation and marketization, and thereby highlights the wider policy and regional theory context of their production to frame the structural factors impacting the rewriting of city regional space. By doing so, we find a number of issues with the current decentralisation approach in competing priorities between localities, an over-reliance on agglomeration economies and urban competition, potential mismatches in scales of policy decision-making and delivery, and challenges regarding inequalities in a post-Brexit England

Mobile phone indicators and their relation to the socioeconomic organisation of cities

Thanks to the use of geolocated big data in computational social science research, the spatial and temporal heterogeneity of human activities are increasingly being revealed. Paired with smaller and more traditional data, this opens new ways of understanding how people act and move, and how these movements crystallise into the structural patterns observed by censuses. In this article we explore the convergence of mobile phone data with more classical socioeconomic data from census in French cities. We extract mobile phone indicators from six months worth of Call Detail Records (CDR) data, while census and administrative data are used to characterize the socioeconomic organisation of French cities. We address various definitions of cities and investigate how they impact the relation between mobile phone indicators, such as the number of calls or the entropy of visited cell towers, and measures of economic organisation based on census data, such as the level of deprivation, inequality and segregation. Our findings show that some mobile phone indicators relate significantly with different socioeconomic organisation of cities. However, we show that found relations are sensitive to the way cities are defined and delineated. In several cases, differing city definitions delineations can change the significance or even the signs of found correlations. In general, cities delineated in a restricted way (central cores only) exhibit traces of human activity which are less related to their socioeconomic organisation than cities delineated as metropolitan areas and dispersed urban regions.Comment: 19 pages, 9 figures, 2 table

A New Velocity and Total Suspended Solid Measurement Device

The quality of field measurements in sewer systems relies on the spatial representativeness of the measurements. This study aims at field measurements of both velocity and total suspended solids (TSS) using a two dimensional sampler called Hydre. The device was implemented, tested and used in a sewer system for a range of hydraulic situations. This paper presents the principles of development and conception of the instrument. Analyses of the results demonstrate the ability of the device to provide robust TSS and velocity profiles in sewers for a range of flow conditions. L’évaluation des flux de polluants transitant dans les réseaux d’assainissement dépend notamment de la représentativité spatiale des mesures de vitesses et de concentrations en matières en suspension. Cette problématique a été étudiée expérimentalement par des mesures dans des réseaux urbains. Un échantillonneur bidimensionnel, appelé Hydre, a été développé et installé dans un collecteur. Il a permis d’étudier la répartition spatiale des vitesses et des concentrations pour une large gamme de contextes hydrauliques. Cet article présente la conception de cet échantillonneur. Les résultats sont présentés et discutés. Ils montrent la bonne homogénéité des concentrations dans la section mouillée