Monocentric Versus Polycentric Models in Urban Economics

This article overviews the development of the formal modelling framework for the urban spatial structure which started in 1960s and grew dramatically thereafter. Modelling in the 1970s focused on the endogenous formation of the central business district within a city. Then richer polycentric city models were developed in 1980s, where the number, location and spatial extent of the business districts are determined endogenously. The emergence of the new economic geography in 1990s provided a framework capable of explaining the spatial distribution of cities (rather than the business districts within a city) and their industrial structure in a general location-equilibrium model.

An Industrial Agglomeration Approach to Central Place and City Size Regularities

An empirical regularity designated as the Number-Average Size (NAS) Rule was first identified for the case of Japan by Mori, Nishikimi and Smith [13], and has since been extended to the US by Hsu [6]. This rule asserts a negative log-linear relation between the number and average population size of cities where a given industry is present, i.e., of industry-choice cities. Hence one of its key features is to focus on the presence or absence of industries in each city, rather than the percentage distribution of industries across cities. But despite the strong empirical regularity of this rule, there still remains the statistical question of whether such location patterns could simply have occurred by chance. In this paper an alternative approach to industry-choice cities is proposed. This approach utilizes the statistical procedure developed in Mori and Smith [15] to identify spatially explicit patterns of agglomeration for each industry. In this context, the desired industry-choice cities are taken to be those (economic) cities that constitute at least part of a significant spatial agglomeration for the industry. These cluster-based choice cities are then used to reformulate both the NAS Rule and the closely related Hierarchy Principle of Christaller [2]. The key empirical result of the paper is to show that the NAS Rule not only continues to hold under this new definition, but in some respects is even stronger. The Hierarchy Principle is also shown to hold under this new definition. Finally, the present notion of cluster-based choice cities is also used to develop tests of both the locational diversity of industries and the industrial diversity of cities in Japan.

A Reconsideration of the NAS Rule from an Industrial Agglomeration Perspective

An empirical regularity designated as the Number-Average Size (NAS) Rule was first identified for the case of Japan by Mori, Nishikimi and Smith [71], and has since been extended to the US by Hsu [50]. This rule asserts a negative log-linear relation between the number and average population size of cities where a given industry is present, i.e., of industry-choice cities. Hence one of its key features is to focus on the presence or absence of industries in each city, rather than the percentage distribution of industries across cities. But despite the strong empirical regularity of this rule, there still remains the statistical question of whether such location patterns could simply have occurred by chance. Indeed, chance occurrences of certain industry-choice cities may be quite likely if, for example, one includes cities where only a single industrial establishment happens to appear. An alternative approach to industry-choice cities is proposed in a companion paper, Mori and Smith [73], which is based on industrial clustering. More specifically, this approach utilizes the statistical procedure developed in Mori and Smith [72] to identify spatially explicit patterns of agglomeration for each industry. In this context, the desired industry-choice cities are taken to be those (economic) cities that constitute at least part of a significant spatial agglomeration for the industry. With respect to these cluster-based industry-choice cities, the central objective of the present paper is to reconfirm the persistence of the NAS Rule between the years 1981 and 2001, as first observed in Mori et al. [71]. Indeed the NAS Rule is in some ways stronger under this new definition of industry-choice cities in that none of outlier industries in the original analysis show any significant agglomeration, and hence can be excluded from the present analysis. A second objective is to show that there has been a substantial churning of the industry mix in individual cities between these two time periods, and hence that persistence of the NAS Rule is even more remarkable in this light. Finally, these persistence results are extended to both the Rank Size Rule and the Hierarchy Principle of Christaller [13], which were shown in Mori et al. [71] to be intimately connected to the NAS Rule.

Increasing Returns in Transportation and the Formation of Hubs

The spatial structure of transport network is subject to increasing returns in transportation, distance and density economies. Transport costs between locations are thus in general endogenous, and are determined by the interaction between the spatial distribution of transport demand and these increasing returns, although such interdependence has long been ignored in regional models. By using a simple model, the present paper explains the formation of transport hubs endogenously, and shows how the balance of these two types of increasing returns influences the spatial distribution of transport hubs.Formation of a transport hub, Distance economies of transportation, Density economies of transportation

Increasing Returns in Transportation and the Formation of Hubs

The spatial structure of transport networks is subject to increasing returns in transportation, distance, and density economies. Transport costs between locations are thus, in general, endogenous, and are determined by the interaction between the spatial distribution of transport demand and these increasing returns, although such interdependence has long been ignored in regional models. By using a simple model, the present paper investigates the characteristics of viable hub structures (in terms of spacing and hierarchical relations) given the presence of density and distance economies in transportation.

Frontiers of the New Economic Geography

This paper presents an overview of recent development in the new economic geography (NEG), and discusses possible directions of its future development. Since there already exist several surveys on this topic, we focus on the selected features of the NEG which are important yet have attracted insufficient attention, and also on the recent refinements and extensions of the framework