Recently, urban dynamics lab Research Associate, Clémentine Cottineau, based at CASA attended the URBANICS III workshop in Chile and presented her work on a dynamic meta-analysis of Zipf’s law. URBANICS is an interdisciplinary workshop on Urban Dynamics organised by a team of geographers, economists, mathematicians and computer scientists in Chile. This third version took place in Pucón from March 13th to March 16th and aimed at defining a research agenda on urban dynamics for the future. The discussion resolved around urban networks, city dynamics theory and empirical models using big data. The small lakeside town near the Villarrica Volcano provided a beautiful natural environment to stimulating debates and collaboration opportunities.
Clementine says about her talk at the conference: “The results from urban scaling in recent years have hold the promise of increased efficiency to the societies which could actively influence the distribution of their cities’ size. However, little evidence exist as to which factors influence the level of urban unevenness, expressed by the slope of the rank-size distribution, partly because of the diversity of results found in the literature following the heterogeneity of estimations specifications. In this study, I set up a meta-analysis of Zipf’s law which account for technical as well as topical factors of deviation of this measure of unevenness. I found 86 studies publishing at least one empirical estimation of Zipf’s coefficient and recorded their metadata in an open database. I then regressed the 1962 resulting estimates with variables describing the study and estimation process as well as with socio-demographic variables describing the territory under enquiry. A dynamic meta-analysis was also performed to look for factors of evolution of city size unevenness. Only the results of the most interesting models are presented, but all analyses can be reproduced on a dedicated online platform. The results show that on average, 50% of the variation of Zipf’s coefficients is due to the technical choices of estimation. For the rest, the main variables associated with distinct evolutions are linked to the urbanisation process rather than economic development or population growth. The pace at which cities are added to the system for instance seems to be the best predictor of the evolution of unevenness, although most variation still remained unexplained. This seems to leave space for planning actions, even though we find that unplanned outcomes of rebalancing policies is historically the rule rather than the exception.”