This paper shows that the standard continuous-time core-periphery model (the foundation of the New Economic Geography) is not robust; simply reformulating it in discrete time has profound implications. The continuous-time model can only exhibit stationary long-term behavior, and high transport costs are perceived as stabilizing. In contrast, the discrete-time model can exhibit cycles of any periodicity or chaotic behavior, and high transport costs are de-stabilizing. Furthermore, the sensitive dependence of long-term behavior on initial conditions and on parameters is so acute and so pervasive that it seriously calls into question reliance on propositions derived from the continuous-time model.

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We provide empirical evidence on the network structure of trade flows between European regions and discuss the theoretical underpinning of such a structure. First, we analyze EU regional trade data using Social Network Analysis. We describe the topology of this network and compute local and global centrality measures. Finally, we consider the distribution of higher order statistics, through the analysis of local clustering and main triadic structures in the triad census of interregional trade flows. In the theoretical part, we explore the relationship between trade costs and trade links. As shown by Behrens (2004, 2005a, 2005b) in a two-region linear new economic geography (NEG) model, trade costs and the local market size determine, even with finite trade costs, unconditional autarky and unilateral trade, that is, a one-directional flow from one region to the other. Following these contributions and guided by the empirical evidence, we clarify the relationship between market competition, trade costs and the patterns of trade in a three-region NEG model. We identify a larger set of trade network configurations other the three elementary ones that occur at the dyadic level between two regions (no trade, one-way trade, reciprocated two-way trade), and relate the model with the triad census.

Using intra-European interregional trade data, we analyze the topology of the E.U. regional trade network. A triad census analysis confirms the intuition that the interregional trade network (and, thus, the European economic integration) is far from being complete. The majority of the E.U. interregional trade patterns are characterized by simple, at best bilateral, configurations. Moreover, we analyze the effect of trade costs in shaping the topological structure of the network. It emerges that the relative presence of simple trade configurations increases with distance, while the relative presence of more complex trade configurations decreases with distance. Finally, we discuss the theoretical underpinnings of these empirical facts through a simple new economic geography model with three regions. In this model, we analyze how trade costs shape the pattern of the trade network. On the whole we find a correspondence between theoretic and empirical results. However, details differ and they suggest directions for further research

This paper examines the long-term behaviour of a discrete-time Footloose Capital model, where capitalists, who are themselves immobile between regions, move their physical capital between regions in response to economic incentives. The spatial location of industry can exhibit cycles of any periodicity or behave chaotically. Long-term behaviour is highly sensitive to transport costs and to the responsiveness of capitalists to profit differentials. The concentration of industry in one region can result from high transport costs or from rapid responses by capitalists. In terms of possible dynamical behaviours, the discrete-time model is much richer than the standard continuous-time Footloose Capital model.