研究内容
大都市はなぜ,どこに生まれ,どのように成長するのでしょうか.ひとつの大都市のなかで,なぜ,どこに都心が形成されるのでしょうか.私の研究の関心は,ミクロ経済学およびゲーム理論を分析ツールとして,大都市の形成のように人の行動が生み出す空間的なパターンを表現・分析・理解し,政策評価に結びつけることにあります.都市・地域政策の経済評価には,人口・経済活動の空間分布の長期的な変化を考慮することが欠かせません.例えば,高速道路・新幹線のような交通基盤整備は,人口の空間的な集積・分散に多大な影響を及ぼしてきました.それらの現象が起こる背景にあるメカニズムの理解とその表現は,信頼できる長期的な政策評価の前提です.大都市への人口・経済活動の集中や,都市内における土地配分など,空間上における現象の多くは,たくさんの主体の意思決定の結果として現れたものと捉えられ,経済学理論は理解を深めるための有効な分析手段です.
主要成果
Osawa, M., & Akamatsu, T. (2020). Equilibrium refinement for a model of non-monocentric internal structures of cities: A potential game approach. Journal of Economic Theory, 187, 105025.
Using the theory of potential games, this paper addresses the emergence of polycentric structures in cities that result from trade-offs between agglomeration economies and congestion effects. We consider a model that explains the formation of multiple business centers in cities as an equilibrium outcome under the presence of households’ commuting costs and positive technological externalities between firms. We show that the model is a large-population (non-atomic) potential game. To elucidate properties of stable spatial equilibria in the model, we consider local and global maximizations of the potential function, which are known to correspond to various equilibrium refinement criteria. We find that (i) the formation of business centers (agglomeration of firms) is possible only when households’ commuting costs are sufficiently low and that (ii) the size (number) of business centers increases (decreases) monotonically as communication between firms becomes easier.
Osawa, M., Fu, H., & Akamatsu, T. (2018). First-best dynamic assignment of commuters with endogenous heterogeneities in a corridor network. Transportation Research Part B: Methodological, 117, 811-831.
Osawa, M., Akamatsu, T., & Takayama, Y. (2017). Harris And Wilson (1978) Model Revisited: The spatial period-doubling cascade in an urban retail model. Journal of Regional Science, 57(3), 442-466.