The dysfunction of urban planning that has been premised on suppressing negative externalities has been increasingly pointed out． For future urban planning，it is necessary to establish approaches that，through interventions from both the information space and the urban space—such as information provision and the targeted guidance of individual stores—coordinate the expectations of various actors in the city，generate positive externalities，and thereby create distinctive area identities． How does urban “metabolism”—the emergence, growth, and decline of places—occur, and through what mechanisms? Is it possible to manage these processes? Based on these questions, I am currently conducting research to elucidate the mechanisms of urban formation from three perspectives: (1) evaluating the characteristics of established areas, (2) understanding the decision-making processes of urban actors underlying area formation, and (3) developing policy and planning interventions to encourage the activities of urban actors that generate positive externalities in cities.
Positive externalities based on synergy and complementarity among neighboring stores are a major mechanism that drives the agglomeration of stores in commercial districts and shapes area characteristics.
From such spatial co-occurrence relationships among stores, this study inferred latent store attributes that can explain the micro-level mechanisms of retail agglomeration.
The estimated latent attributes exhibited greater explanatory power than commonly used store categories, suggesting their usefulness as a new basis for classifying stores. In addition, by comparing major commercial districts across Japan. I identified co-occurrence patterns of shared latent attributes and revealed universal spatial structures underlying store agglomeration in commercial areas．
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In general, rankings and reviews—information that aggregates the evaluations and choices of many people—are regarded as beneficial collective intelligence that supports individual decision-making and benefits society. The purpose of this study is to re-examine this premise, to show that collective intelligence can, under certain conditions, have negative effects on urban space and consumer behavior, and to theoretically and empirically elucidate the underlying mechanisms.
In this study, I refer to this negative effect of collective intelligence as an “overfitted inferior equilibrium” and define it as a state in which, despite the availability of diverse options，repeated decision-making based on collective intelligence concentrates choices on particular options (i.e., overfitted)，thereby reducing social efficiency (i.e., an inferior equilibrium)．
To examine this phenomenon, I developed an agent-based model and a theoretical model that incorporate behavioral principles of individuals (demand-side agents) and stores (supply-side agents) in an urban system, and analyzed the conditions under which it emerges and the mechanisms through which it operates．
The results show that when (1) individual preferences are heterogeneous, and (2) majority choices are emphasized as popularity information and are imitated by both individuals and stores, then (3) individuals become less able to find stores that match their preferences, stores also become less able to attract customers who match them, and social efficiency declines.
Through these analyses, this study systematically clarifies the formation mechanism of the overfitted inferior equilibrium, showing not only that “mutual imitation by both individuals and stores” is a key driver of its emergence, but also that “switching costs” and “inter-store competition” function as factors that suppress it.
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