Shusuke Ioku
井奥 崇輔
Welcome to my website. I am a Ph.D. candidate in Political Science at the University of Rochester, specializing in historical political economy. I study state building and political extremism, combining formal theory with micro-level geographic and individual data. My current projects examine how competitive governance can constrain state extraction by enabling mass exit as an alternative to violent rebellion, how governments use land reform to build support for totalitarian regimes, and the origins of feudalism.
Email: sioku[at]ur.rochester.edu
RESEARCH
Constrain with Their Feet: Jurisdictional Rivalry and State Erosion in Early Modern Japan
Under Review DOWNLOAD
Abstract. Throughout history, jurisdictional conflict among rival rulers has constrained oppression by enabling subjects to pursue mass exit—often to draw external intervention—as an alternative to directly confronting authority. I document this mechanism in Tokugawa Japan, where a feudal structure of domains with similar institutions but divergent tax burdens competed for subjects’ loyalty, creating an ideal setting to observe a competitive market for governance. Leveraging newly digitized village-level records of peasant resistance, I show that exposure to alternative authority—measured by the ratio of a village’s distance to its home-domain capital relative to the nearest foreign-domain capital—induced villages to opt for exit over confrontation. Moreover, domains facing more intense jurisdictional rivalry—measured by the average distance ratio across their villages—extracted lower taxes, accounting for alternative mechanisms. These findings highlight mass exit as an active means of popular constraint, surfacing a mechanism long overshadowed by scholarship’s emphasis on direct resistance and notions of passive exit.
Self-State Subversion: The Birth of Feudalism in Early Medieval Japan
Work In ProgressAbstract. While scholars broadly agree that feudal orders arose from the limitations of centralized state control, much less is known about the mechanisms through which this process began and unfolded—specifically, who fostered the fragmentation of state power and where it originated. I propose a theoretical framework identifying the conditions under which statebuilders deliberately hollow out their own administrative apparatus by privatizing extraction: granting fiscal immunities in exchange for a share of the returns. I evaluate the model’s implications using the case of early medieval Japan, where varying degrees of feudalization across regions can be systematically observed through estate commendations to the imperial court. Consistent with the theory, I find that estate commendation by emerging local warrior elites occurred most prominently in peripheral regions where central authority was weak but local administrative capacity remained strong.
Thought Police: Theory and Evidence of Ideological Repression
Work In ProgressAbstract. Autocratic regimes frequently employ repression to target specific groups of citizens. This paper examines state repression directed at particular ideologies—a form of control that creates unique enforcement challenges. Since individuals’ ideological commitments are unobservable to authorities, thought repression generates a fundamental information problem compounded by pooling incentives among dissidents. Under this endogenously reinforced information asymmetry, optimal state repression exhibits a tendency toward increasing indiscrimination. I develop this theoretical logic through a formal model of ideological oppression and provide empirical support using evidence from communist repression by Japan’s special higher police between 1911 and 1945. Employing an event-study design with original individual-level data on 16,811 activists, I demonstrate two concurrent trends: over time, dissidents both with and without radical ideologies became equally likely to engage in organizational activities, while the government’s repression strategy became increasingly indiscriminate on both low- and high-profile citizens.
Hydraulic Civilizations
Work In ProgressAbstract. Although agricultural surplus was vital for early state formation, it also exposed states to external threats. I claim that while surplus itself jeopardized states, the administrative capacity to generate it—specifically hydraulic management—promoted state persistence. Maintaining costly irrigation systems provided rulers with bargaining leverage over both external predators and internal subjects, deterred both invasions and defections, and thereby fostered stable territorial control. I illustrate this argument through a formal model and test it using global data of historical polities since 3400 BCE. Duration analysis shows that states with greater hydraulic dependence, measured by the potential yield gap between irrigated and rainfed farming, tended to endure longer without losing territories, while higher absolute yields accelerated territorial loss. The result was exclusively found in earlier periods, where developing hydraulic systems was more costly. Additionally, polities with greater hydraulic dependence tended to develop more complex social structures.
Military Innovation and Territorial State Formation
Abstract. Social scientists have argued that conflict and military technological innovation fostered the formation of territorial states. While the literature has predominantly examined European history, Japan’s Warring-States Period offers a unique context to test this claim; the island country initially composed by more than 100 autonomous local powerholders (daimyo) was exposed to an exogenous shock of military innovation, an accidental importation of firearms in 1543, after which the fragmented society rapidly transformed into a centralized state under a singular authority. Using original grid-year datasets of battles, castles, and territorial changes, we show (preliminary, descriptive) results suggesting that the technological shock diminished defensive advantage and made economic power better translate into battleground success, thereby inducing small rulers to concede their autonomy.
外交の計量分析：外交使節制度の衰微と再生
A book chapter in 『国際関係研究の方法』（東京大学出版会）
Published in 2021
TALKS
- Weapons of the Weak
MPSA 2025; JSQPS 2024 Summer
- Teppo Made Japan
Waseda University, 2023
- Empirical Model of Alliance Formation
Waseda University, 2022
- Threats and Assurances in Crisis Bargaining
MPSA 2021
AWARDS & GRANTS
- Best Paper/Presentation Award
2024, Graduate Seminar, Department of Political Science, University of Rochester
- Best Graduation Thesis Award
2021, Waseda University
TEACHING
- TA for ECO 288, Game Theory
2025 Spring, Prof. Tasos Kalandrakis, University of Rochester
2024 Spring, Prof. Romans Pancs, University of Rochester - TA for ECO 255, Poverty and Development
2024 Fall, Prof. Anderson Frey, University of Rochester
- TA for PSCI 407, Mathematical Modeling
2023 Fall, Prof. John Duggan, University of Rochester
A core method course in the Political Science Ph.D. program - TA for 国際政治学
2021 Spring, Prof. Shuhei Kurizaki, Waseda University
EDUCATION
- University of Rochester (Aug 2021 - Present)
Ph.D. in Political Science
Major: Formal Theory, International Relations
Advisors: Scott F. Abramson, Casey Petroff, Hein Goemans, Sergio Montero - Waseda University (Apr 2020 - Aug 2021)
M.A. in Political Science
Advisors: Shuhei Kurizaki, Atsushi Tago - University of Tokyo (Apr 2011 - Aug 2017)
B.A. in Philosophy + M.P.P