要旨：Cities and roads are the fundamental infrastructures that human society has developed. Their organizations are complex phenomena involved with many natural and social factors: business, commerce, transport, politics, diplomacy, culture, landscape, climate, hydrosphere, natural resources, etc. Geographical landscape appears to be the key factor among them, but most previous modelling studies assumed an ideally homogeneous space because of so-called `for the sake of simplicity'. Here we propose a working hypothesis that co-evolving dynamics of cities and roads defined on the space of geographical landscapes reproduce the outline of real-world spatial patterns of them. To examine this hypothesis, using high resolution digital topographic databases, we evaluate the distance between locations on the natural terrains by least cost path analysis, and define a dynamical system of the cites and roads on the evaluated space, and compare the stationary state of the system with a census. In a preliminary work on Hokkaido region in Japan, we found that the integration of the natural geographical factors leads to the emergence of comparable spatial patterns to the real one, while the model also reproduces the regularly spaced, lattice-like pattern of cities as the same as the previous models on an ideally homogeneous space with a homogeneous city-size distribution. This result indicates that the natural landscape factors have important relevance on the spatial distribution of populations.

要旨：In the early 20th century, the British Empire primarily governed South Asia, and these regions shared similar administrations, institutions and commercial practices. After the Second World War, decolonization in South Asia became evident through the partition of India and countries gaining independence. These subsequent events can be seen as regional disintegration, and they offer a potential scope for examining the impacts of such institutional changes on maritime transport networks. By examining a new database detailing vessel movement between South Asian ports and the rest of the world from 1890 to 2000, we explore how maritime transport networks evolved in South Asia. Specifically, we compare the trends of shipping routes among ports before and after 1947. Applying the methodology developed by Redding, Sturm, and Wolf (2011) and Xu and Itoh (2017), we show that regional disintegration clearly lowered vessel movements for the routes that became international after 1947. Additionally, we examine two points; relationship with UK, and the independence of Bangladesh. For most of the cases, we find significantly negative impacts on vessel movements directly affected by regional disintegration.

要旨：This paper aims to theoretically and empirically investigate the relationship between agglomeration and urban industrial upgrading. If the high-tech industries relied on skilled labor, R&D, and specialized services more intensively, and the major channels of agglomeration economies were labor pooling, knowledge spillovers, and sharing the specialized local services, then urban agglomerations will gain comparative advantage and relatively specialize in the production of high-tech goods. Based on the urban industrial grade index developed in this paper, the association between agglomeration and urban industrial upgrading is confirmed by a panel regression using the data of Japan cities.

要旨：I propose a model with multiple cities that allows inter-city interactions through costly trade, internal migrations, and firm relocation. The model features multiple sectors, heterogeneous firms, and heterogeneous workers. The comparative statics of the model focuses on three shocks: falling transport costs, declining education costs, and increasing high-skill intensities. I show that: (1) there is a non-monotonic relationship between transport costs and the spatial income inequality; (2) a structural transformation triggered by declining education costs reduces the inequality, (3) the one due to a skill-biased technological change, however, predicts the opposite. The theoretical predictions are confirmed by a panel regression using the data from 32 countries with 1,962 regions.

要旨：This paper shows evidence for a microeconomic mechanism of collaborative knowledge creation proposed by Berliant and Fujita (2008) using the panel data of patent development in Japan. Researchers communicate via common knowledge, and innovate by utilizing differentiated knowledge of each other. A longer duration of collaboration between a pair of researchers increases their common knowledge which at the same time accumulates differentiated knowledge between them and the rest of the researchers. Facing polyadic interactions, individual researchers collectively determine the set of collaborators to interact, and hence the fraction of time a researcher spends with each of her collaborators, so as to optimize the composition of common and differentiated knowledge between a given researcher and each of her collaborators. We also show additional evidence for creative destruction, positive influence of local spillovers as well as transport accessibility.