3月の研究業績

OSIPP基幹講座教員の2月の研究業績をご紹介します。
・前川和歌子先生　
・髙田陽奈子先生　
・二杉健斗先生　
・松島法明先生　
・西山克彦先生

Wakako Maekawa, Hinako Takata（論文）
"External Influence on Latin America’s ‘Peace-Versus-Justice’Dilemma: 
(How) Do Inter-American Court of Human Rights Anti-Amnesty Law Judgments Affect Peace and National Reconciliation?"
International Journal of Transitional Justice, 24 February 2026(査読有)
DOI: https://doi.org/10.1093/ijtj/ijag004

Abstract: Judgments of the Inter-American Court of Human Rights (IACtHR) that hold amnesty laws illegal under the American Convention on Human Rights (‘anti-amnesty law judgments’) have often been criticized for excessively prioritizing human rights and justice over peace and national reconciliation. This study empirically examines how the IACtHR should address this ‘peace-versus-justice dilemma.’ Using IACtHR judgments from 2003 to 2019 and case studies of Peru and El Salvador, we analyze the impact of the IACtHR’s anti-amnesty law judgments on peace and national reconciliation in Latin American societies, focusing on protests against governments and polarization as early indicators of civil conflict. Our findings suggest that although the IACtHR’s anti-amnesty law judgments do not necessarily undermine peace and national reconciliation directly, the IACtHR should address the resultant long-term political and social polarization as a potential factor in social destabilization that could lead to civil conflict.


Wakako Maekawa（論文）
Wakako Maekawa and Theodora-Ismene Gizelis
"Trading peace for hazard management? peace agreement implementation and United Nations peace operations during natural hazards"
World Development, vol.203, 2026-03-19(査読有)
doi: https://doi.org/10.1016/j.worlddev.2026.107387

Abstract: Although United Nations Peace Operations (UNPOs) can strengthen capacity and improve responses to natural hazards, the core peace operation and ability to produce peace can become victims of crisis management success. Natural hazards can impede UNPOs’ activities and peace accord implementation through three mechanisms: 1) UNPOs activities are diverted to immediate humanitarian assistance, away from core UNPOs’ activities; 2) changes to the bargaining process; and 3) lower opportunity costs of violence and increased opportunities to renege on agreements or call for renegotiations. We compare peace agreement implementation with UNPOs versus peace agreement implementation without UNPOs when facing natural hazards. In an analysis of countries with comprehensive peace agreement implementations between 1992 and 2015 we find that natural hazards during UNPOs deployment see lower subsequent peace agreement implementation relative to hazards in countries without UNPOs. We see these findings as consistent with greater dependency on UNPOs, creating greater tension between responses to natural hazards and peace implementation. Further analysis to unpack the three mechanisms suggests support for the first two mechanisms.

二杉健斗 （論文）
「国際投資法と持続可能な発展のディスクール――なぜ「調和」の論理が「対立」を生むのか――」世界法年報46号（2026年）162-187頁 

概要：世界法学会2025年度研究大会（統一テーマ「国際法における環境法的思考の可能性―持続可能性を統合するグローバルな法システムの課題―」）での報告をもとにした原稿。本稿は、国際投資法と環境保護をめぐる「対立言説」（投資仲裁が環境規制を萎縮させるという批判）と「調和言説」（投資法は正当な規制を尊重し環境と両立するという主張）の緊張関係が生じる原因を、知識社会学・科学社会学の視座を用いて分析した。この対立は、調和言説の法的根拠の欠如でも、批判者側の法的知識の欠如によるものでもなく、むしろ何が「正当」な規制かを決定する権力が投資法側に偏在していることへの異議申立てに起因すると論じている。

Noriaki Matsushima（DP）
Noriaki Matsushima, Kazuki Nishikawa, Jiaying Qiu “The effects of minimum wage in inter-regional duopoly competition”
OSIPP Discussion Paper: DP-2026-E-001, March 24, 2026
https://www.osipp.osaka-u.ac.jp/archives/DP/2026/DP2026E003.pdf
https://hdl.handle.net/11094/104192

Abstract: A binding minimum wage can raise the regulated firm's profits when labor-market power interacts with product-market competition. 
We develop a duopoly model in which firms compete in the same product market but hire workers from distinct, geographically segmented labor markets. Because the minimum wage applies only to one firm's labor market, it does not directly raise its rival's costs. With monopsony power, the minimum wage reduces the regulated firm's marginal cost and induces it to expand output, forcing its rival to contract through strategic interaction. Under Cournot competition, this mechanism also increases total employment and consumer surplus.


Katsuhiko Nishiyama（DP）
“The Impact of Job Displacement on Health Insurance Status in the post-ACA Era”
OSIPP Discussion Paper: DP-2026-E-001, February 27, 2026
https://www.osipp.osaka-u.ac.jp/archives/DP/2026/DP2026E001.pdf

Abstract: This paper examines whether insurance sources expanded under the Affordable Care Act (ACA), particularly health insurance marketplaces and Medicaid, compensate for the loss of employer-sponsored health insurance (ESHI) following job displacement. Using monthly data from the 2014--2016 Survey of Income and Program Participation, I estimate duration-specific effects of displacement on each coverage source with a difference-in-differences design. ESHI coverage falls by 15 to 18 percentage points within a few months of displacement, with only slight recovery over the following year. Medicaid enrollment increases modestly, driven entirely by workers in expansion states where coverage increases exceed 7 percentage points. Directly purchased private insurance shows no discernible response despite marketplace availability and premium subsidies, and this holds across income levels. These findings indicate that ACA marketplace reforms in the sample period provide limited protection for displaced workers.