My research investigates how cities and regions function within mature economies. The main focus is on the empirical analysis of agglomeration economies, borrowed size, interregional networks, productivity, efficiency, regional resilience, and energy use. 

The research program combines regional science, urban and regional economics, spatial econometrics, productivity analysis, DEA/SFA-based efficiency analysis, and applied policy analysis.  

1. Agglomeration economies and borrowed size 

2. Regional productivity, efficiency, and sustainability 

3. Regional resilience and spatial interdependence 

4. Energy economics and regional environmental performance 

The articles below highlight key empirical and conceptual contributions at successive stages of this research program. 

Foundations and Transition: Agglomeration Economies, Accessibility, and Energy Efficiency 

• Otsuka, A., Goto, M., & Sueyoshi, T. (2010). Industrial agglomeration effects in Japan: Productive efficiency, market access, and public fiscal transfer. Papers in Regional Science, 89(4), 819–840.

• Otsuka, A., & Goto, M. (2015). Estimation and determinants of energy efficiency in Japanese regional economies. Regional Science Policy & Practice, 7(2), 89–101.

• Otsuka, A. (2018). Dynamics of agglomeration, accessibility, and total factor productivity: Evidence from Japanese regions. Economics of Innovation and New Technology, 27(7), 611–627.

Inter-regional Networks, Productivity, and Regional Sustainability 

• Otsuka, A. (2020). Inter-regional networks and productive efficiency in Japan. Papers in Regional Science, 99(1), 115–133.

• Otsuka, A. (2022). Assessment of the improvement in energy intensity by the new high-speed railway in Japan. Asia-Pacific Journal of Regional Science, 6(1), 267–282.

• Otsuka, A. (2024). Effects of regional network economies on industrial productivity in Japan: Dynamic total factor productivity function approach. Asia-Pacific Journal of Regional Science, 8(4), 1111–1134.

Borrowed Size, Agglomeration Shadows, and Regional Innovation 

• Otsuka, A. (2025). Borrowed size and agglomeration shadows in Japan: A spatial econometric analysis of regional productivity. Asia-Pacific Journal of Regional Science, 9(4), 1115–1144.

• Otsuka, A. (2025). An assessment of the borrowed size effect on the regional innovation system in Japan: A stochastic frontier analysis. The Annals of Regional Science, 74(4), Article 100. 

Conceptual Synthesis and Middle-Range Theory: Borrowed Size in a Mature Economy 

• Otsuka, A. (2025). A three-layer model of borrowed size: Empirical insights from Japan. Regional Studies, Regional Science, 12(1), 975–995.

• Otsuka, A. (2026). Revisiting new economic geography: Borrowed size in Japan’s mature economy. Regional Studies, Regional Science, 13(1), Article 2722818.

A Springer Monograph Trilogy on Regional Economies in Japan 

These three single-authored monographs constitute a cumulative research program. The first examines agglomeration economies through productivity analysis; the second extends the framework to inter-regional networks and regional sustainability; and the third integrates borrowed size, spatial spillovers, innovation, and regional resilience in a mature economy. 

1. A New Perspective on Agglomeration Economies in Japan: An Application of Productivity Analysis (2017)

2. A New Driver of Regional Sustainability in Japan: Inter-regional Network Economies (2021)

3. Borrowed Size and Regional Resilience: Lessons from Japan (2026)

Research Notes on the Monograph Trilogy

To support reading across the three volumes, the following research notes provide an overview of the trilogy and clarify its conceptual and empirical links. 

The English-language note provides a conceptual overview of the trilogy, while the Japanese-language note offers a descriptive synthesis of the empirical puzzle underlying the research program and discusses its implications for Japan’s population-declining economy. 

• Otsuka, A. (2026). From Agglomeration Economies to Borrowed Size: Relational Scale, Network-Based Convergence, and Regional Resilience in Japan’s Mature Economy. Available at SSRN

• Otsuka, A. (2026). 人口減少下の日本における地域経済パズル: 集積の経済から地域間ネットワーク経済を経て Borrowed Size へ至る読解地図 [Japan’s Regional Economic Puzzle under Demographic Decline: A Reading Map from Agglomeration Economies through Interregional Network Economies to Borrowed Size]. Available at Jxiv.

SpringerBriefs in Energy 

This SpringerBrief presents an empirical analysis of regional energy demand and energy efficiency in Japan, linking energy economics, environmental policy, and regional economic analysis.

1. Regional Energy Demand and Energy Efficiency in Japan: An Application of Economic Analysis (2017)

A complete publication record is available through ORCID, researchmap, and  the Yokohama City University Researcher Database.

ORCID | researchmap | Yokohama City University Researcher Database