戰後的日本與德國皆以隨收隨付制（PAYG）為基礎重建大型公共年金制度，並將老年經濟安全與在擴張中的勞動市場中長期繳費的歷程相連結。兩國如今皆面臨快速人口老化，但在外籍勞動力的規模與結構上出現明顯分歧：德國逐步發展為高移民國家；日本則在戰後大多數時期維持相對小規模且高度管制的外國居民人口，直到近年才擴大勞動移民管道。本論文的研究問題為：在戰後日本與德國的比較中，外籍勞動力如何影響兩國的隨收隨付制公共年金制度，並從兩個相互連動的面向加以檢視：永續性（在人口老化下，PAYG 年金制度維持長期融資能力的財務能力）與公平性（對外籍勞工退休保障之分配結果）。

在方法上，本研究採比較歷史制度分析設計，時間範圍涵蓋 1945 至 2025 年。研究結合長期描述性資料序列（外國居民存量與年金制度總體指標）與制度分析，追蹤外籍勞工如何進入受年金覆蓋之就業、累積繳費年資、取得（或未能取得）給付資格，以及退出制度。本文特別聚焦兩項機制：（1）日本形式上屬於「暫時性」方案中的定居動態，即重複入境、政策階梯與家庭錨定如何延長居留；（2）與返國移動及退費規則相關的年金流失（pension leakage），並比較日本的一次性退還金管道，與德國較為嚴格的退費邏輯，以及透過歐盟協調與雙邊安排所形成之相對較強的可攜性。

綜合兩國個案，本文分析指出，移民對年金制度的影響，與其說取決於人數規模本身，不如說更取決於制度設計，尤其是涵蓋規則、典型受保職涯長度、可攜性，以及退出選項所形成的誘因。這些制度特徵可能產生一種權衡：制度在短期內獲得繳費收入，但部分移民累積到的年金權益較弱。本文最後釐清外籍勞動力在何種條件下，較可能在不損及分配公平性的前提下，支持隨收隨付制公共年金制度的財務永續性。

---

Post-war Japan and Germany rebuilt large public pension systems around pay-as-you-go (PAYG) finance, linking old-age security to long contribution histories in expanding labour markets. Both now face rapid population ageing, yet they diverged sharply in the scale and structure of foreign labour: Germany evolved into a high-immigration country, while Japan maintained a relatively small and tightly regulated foreign-resident population for most of the post-war era and expanded labour-migration channels only recently. This thesis asks: in a comparison of post-WWII Japan and Germany, how have PAYG public pension systems been influenced by foreign labour, along two linked dimensions; sustainability (the PAYG pension system’s fiscal capacity to maintain financing over time under population ageing) and fairness (distributional consequences for foreign workers’ retirement security).
Methodologically, the study uses a comparative historical-institutional design covering 1945-2025. It combines long-run descriptive series (foreign-resident stocks and pension-system aggregates) with institutional analysis tracing how foreign workers enter covered employment, accumulate contribution histories, qualify (or fail to qualify) for benefits, and exit. Two mechanisms receive focused attention: (1) settlement dynamics within formally “temporary” programmes in Japan, where repeated entry, policy ladders, and household anchors can extend residence, and (2) pension leakage, associated with return migration and refund rules, contrasted between Japan’s lump-sum withdrawal channel and Germany’s more restrictive refund logic alongside comparatively stronger portability through EU coordination and bilateral arrangements.
Across the two cases, the analysis suggests that immigration’s pension relevance depends less on headcounts alone than on institutional design, especially coverage rules, the typical length of insured careers, portability, and the incentives created by exit options. These features can generate trade-offs in which systems receive short-run contributions while some migrants accrue weaker pension entitlements. The thesis concludes by clarifying the conditions under which foreign labour is more likely to support PAYG pension-system fiscal sustainability without undermining distributional fairness.

Alien Registration Act (Act No. 125 of 1952). (Unofficial English translation, as amended to Act No. 152 of 2004). Ministry of Justice, Government of Japan.

Aslanyan, G. (2014). The migration challenge for PAYG. Journal of Population Economics, 27(4), 1023-1038.

Bahal, S. (2024) The Effect of Immigration on Social Security’s Finances. Bipartisan Policy Center. https://bipartisanpolicy.org/explainer/immigration-social-security-solvency/

BAMF (Bundesamt für Migration und Flüchtlinge). (2025). Das Bundesamt in Zahlen 2024: Asyl, Migration und Integration. Nürnberg: BAMF.

BAMF - Bundesamt für Migration und Flüchtlinge. (2024). Lebenssituation und Teilhabe ukrainischer Geflüchteter (Brief Analysis 1/2024). Nürnberg: BAMF.

Berkel, B., & Börsch-Supan, A. (2004). Pension reform in Germany: The impact on retirement decisions (SFB 504 Working Paper No. 04-62). University of Mannheim.

Bonin, H., Raffelhüschen, B., & Walliser, J. (2000). Can immigration alleviate the demographic burden? FinanzArchiv / Public Finance Analysis, 57(1).

Braun, S., & Mahmoud, T. O. (2011). The employment effects of immigration: Evidence from the mass arrival of German expellees in post-war Germany (Kiel Working Paper No. 1725). Kiel Institute for the World Economy.

Braun, S., & Mahmoud, T. O. (2014). The employment effects of immigration: Evidence from the mass arrival of German expellees in postwar Germany. The Journal of Economic History, 74(1).

Brücker, H., & Jahn, E. J. (2011). Migration and wage-setting: Reassessing the labor market effects of migration. Scandinavian Journal of Economics, 113(2), 286-317.

Bundesamt für Migration und Flüchtlinge (BAMF). (2024). Migrationsbericht der Bundesregierung 2023. Nürnberg: BAMF.

Bundesamt für Soziale Sicherung (BAS). (n.d.). Beitragssätze zur gesetzlichen Rentenversicherung ab 1957.

Bundesarbeitsblatt. (1962, February 10). Regelung der Vermittlung türkischer Arbeitnehmer nach der Bundesrepublik Deutschland (Anwerbeabkommen) nebst Anlage

Bundesministerium für Arbeit und Soziales. (2011). Rentenversicherungsbericht 2011. Berlin.

Bundesregierung. (1974, June 10). Antwort der Bundesregierung auf die Kleine Anfrage … betr. Ausländerbeschäftigung (Drucksache 7/2215). Deutscher Bundestag, 7. Wahlperiode. (Cited by Antwort numbers in text.)

Bundesregierung. (1974, June 10). Antwort der Bundesregierung … betr. Ausländerbeschäftigung (Drucksache 7/2215).

Bundesregierung. (2006). Rentenversicherungsbericht 2005 (Deutscher Bundestag Drucksache 16/905). Berlin: Bundesregierung.

Bundesregierung. (2010). Rentenversicherungsbericht 2010. Berlin: Bundesregierung.

Bundesrepublik Deutschland. (2024). Gesetz zur Modernisierung des Staatsangehörigkeitsrechts (StARModG). Bundesgesetzblatt I, Nr. 104 (22 March 2024).

Börsch-Supan, A. (2024). Pension reforms and inequality in Germany (NBER Working Paper No. 32796). National Bureau of Economic Research.

Börsch-Supan, A. H., & Wilke, C. B. (2004). The German public pension system: How it was, how it will be (NBER Working Paper No. 10525). National Bureau of Economic Research.

Börsch-Supan, A., & Quinn, C. (2015). Taxing pensions and retirement benefits in Germany (CESifo Working Paper No. 5636). CESifo.

Börsch-Supan, A., & Schnabel, R. (1999). Social security and retirement in Germany. In J. Gruber & D. A. Wise (Eds.), Social security and retirement around the world (pp. 135-180). University of Chicago Press.

Börsch-Supan, A., Reil-Held, A., & Wilke, C. B. (2008). Saving incentives, old-age provision, and displacement effects: Evidence from the recent German pension reform (MEA Discussion Paper 150-08). Munich Center for the Economics of Aging.

Campbell, J. C., & Ikegami, N. (2003). Japan’s radical reform of long-term care. Social Policy & Administration, 37(1).

Castles, S. (1985). The guests who stayed: The debate on “foreigners policy” in the German Federal Republic. International Migration Review, 19(3).

Castles, S. (1986). The guest-worker in Western Europe - An obituary. International migration review, 20(4).

Chiavacci, D. (2025). Dam break in Japan’s immigration policy: The 2018 reform in a long-term perspective. Social Science Japan Journal, 28.

Clark, R. L. (1991). Retirement systems in Japan (Ralph H. Blanchard Memorial Endowment Series, Vol. IV). Pension Research Council, Wharton School; Irwin.

Committee on the History of Japan’s Trade and Industry Policy RIETI. (2020). Dynamics of Japan’s trade and industrial policy in the post rapid growth era (1980-2000). Springer.

Conrad, H., & Lützeler, R. (2002). German and Japanese Social Policy in Comparative Perspective: An Overview. Aging and Social Policy: A German-Japanese Comparison.

Destatis (Statistisches Bundesamt). (2009). Bevölkerung und Erwerbstätigkeit: Wanderungen 2007 (Fachserie 1, Reihe 1.2, Table 1.1). Wiesbaden.

Deutsche Rentenversicherung Bund. (2019). 130 Jahre gesetzliche Rentenversicherung. Berlin: DRV Bund.

Deutsche Rentenversicherung Bund. (2024a). Work and pension in Germany and Japan.

Deutsche Rentenversicherung. (2024b). Rentenversicherung in Zeitreihen. Ausgabe 2024 (DRV-Booklet 22). Berlin: Deutsche Rentenversicherung Bund.

Dustmann, C., & Frattini, T. (2014). The fiscal effects of immigration to the UK. Economic Journal, 124(580), F593-F643.

Esping-Andersen, G. (1990). The three worlds of welfare capitalism. Princeton University Press.

European Commission. (2015). The 2015 Ageing Report: Economic and budgetary projections for the 28 EU Member States (2013-2060). European Economy 3|2015. Luxembourg: Publications Office of the European Union.

Federal Ministry of Labour and Social Affairs. (2023). BMAs - old-age security in Germany. Webseite des Bundesministerium für Arbeit und Soziales. https://www.bmas.de/EN/Social-Affairs/Old-age-security-in-Germany/old-age-security-in-germany-art.html

Fehr, H., & Jess, H. (2007). Who benefits from the reform of pension taxation in Germany? Fiscal Studies, 28(1).

Fukawa, T. (2006). Sustainable structure of the Japanese public pension system viewed from a Germany-Japan comparison. The Japanese Journal of Social Security Policy, 6(1).

German History Intersections. (1973/2025). Foreign Worker Recruitment Ban (23 Nov 1973).

Goto, J. (2007). Latin Americans of Japanese origin (Nikkeijin) working in Japan (World Bank WPS 4203).

Government of Japan, Cabinet Office. (2004). Section 5: The progress in structural reform in fiscal policy and financial systems (White Paper on the Japanese Economy, 2004). (n.p.).

Graf, J. (2024). Educational and labour migration monitoring: Issuance of residence titles to third-country nationals-Annual report 2023 (Reports on Migration and Integration - Series 1). Nürnberg: Bundesamt für Migration und Flüchtlinge (BAMF), Research Centre.

Göktürk, D., Gramling, D., & Kaes, A. (Eds.). (2007). Germany in transit: Nation and migration, 1955-2005 (Vol. 40). Univ of California Press.

Hansen, G. D., & İmrohoroğlu, S. (2016). Fiscal reform and government debt in Japan: A neoclassical perspective. Review of Economic Dynamics, 21, 201-224.

Hennessey, G., & Hagen-Zanker, J. (2020). The fiscal impact of immigration: A review of the evidence.

Holzmann, R., Koettl, J., & Chernetsky, T. (2005). Portability Regimes of Pension and Health Care Benefits for International Migrants: An Analysis of Issues and Good Practices (Social Protection Discussion Paper No. 0519). Washington, DC: World Bank.

Horlick, M., & Wooten, I. (1979). German provisions for deferred retirement. Social Security Bulletin, 42(6).

Abadie, A. (2005). Semiparametric difference-in-differences estimators. The review of economic studies, 72(1), 1-19.

Immigration Control and Refugee Recognition Act. (1951). Cabinet Order No. 319 of October 4, 1951. [English translation]. Ministry of Justice, Government of Japan.

Immigration Services Agency of Japan (ISA). (2023). Initiatives to Accept Foreign Nationals (policy outline, SSW-i/ii). Tokyo: ISA.

Immigration Services Agency (Japan). (n.d.). (2024). Immigration Control and Residency Management in Recent Years (Part I).

Immigration Services Agency of Japan. (2024). Immigration Control and Residency Management, 2023 - Data Section.

Immigration Services Agency of Japan. (2024). Immigration Control and Residency Management: Data Section 2024. Ministry of Justice.

Insurance and National Pension business, FY2023 (令和5年度 厚生年金保険・国民年金事業の概況).

International Monetary Fund. (2012). Japan: How does macro indexing work? In Japan-Selected Issues (IMF Country Report 12/285).

International Monetary Fund. (2012a). Pension Reforms in Japan (IMF Working Paper 12/285). (Includes Box: “How Does Macro Indexing Work?”).

International Monetary Fund. (2012b). Japan: Selected Issues (IMF Country Report 12/209).

IPSS (National Institute of Population and Social Security Research). (2002). Population Projections for Japan: 2001-2050. Tokyo: IPSS.

IPSS (National Institute of Population and Social Security Research). (2008). Population Statistics of Japan 2008.

IPSS (National Institute of Population and Social Security Research). Table 10.1 Registered Foreigners by Nationality: 1950-2006

IPSS (National Institute of Population and Social Security Research). Table 10.1 Registered Foreigners by Nationality: 1950-2021

İmrohoroğlu, S., Kitao, S., & Yamada, T. (2016). Achieving fiscal balance in Japan. International Economic Review, 57(1).

İmrohoroğlu, S., Kitao, S., & Yamada, T. (2017). Can guest workers solve Japan’s fiscal problems? Economic Inquiry, 55(3).

Japan International Training Cooperation Organization. (2010, October). Technical Intern Training Guidebook for Technical Intern Trainees. Tokyo: JITCO.

Japan Pension Service. (2025). Lump-sum Withdrawal Payment Claim Form (National Pension / Employees’ Pension Insurance) [Pamphlet].

Japan Pension Service. (n.d.). To persons from other countries departing from Japan [brochure].

Japan-Germany Social Security Agreement. (n.d.). 社会保障に関する日本国とドイツ連邦共和国との間の協定.

Jimenez, J. (2014). Illegality from within: The sustenance of migrant illegality in Japan. Electronic Journal of Contemporary Japanese Studies, 14(1), Article 5.

Jürgens, J. (2010). The legacies of labor recruitment: The guest worker and Green Card programs in the FRG. Policy and Society, 29(4).

Kahanec, M., Pytliková, M., & Zimmermann, K. F. (2014). The free movement of workers in an enlarged European Union: Institutional underpinnings of economic adjustment (IZA Discussion Paper No. 8456). Bonn: IZA.

Kalkmann, M. (2017). Country Report: Germany-2016 Update (Asylum Information Database). European Council on Refugees and Exiles.

Kashiwase, K., Nozaki, M. M., & Tokuoka, K. (2012). Pension reforms in Japan. International Monetary Fund.

Kashiwazaki, C., & Akaha, T. (2006). Japanese immigration policy: Responding to conflicting pressures. Migration Information Source. Migration Policy Institute.

Kitao, S. (2014). Sustainable social security: Four options. Review of Economic Dynamics, 17(4).

Kitao, S. (2017). When do we Start? Pension reform in ageing Japan. The Japanese Economic Review, 68(1).

Kitao, S. (2018). Policy uncertainty and cost of delaying reform: The case of aging Japan. Review of Economic Dynamics, 27.

Kosyakova, Y., Brücker, H., Gatskova, K., & Schwanhäuser, S. (2023). Arbeitsmarktintegration ukrainischer Geflüchteter: Erwerbstätigkeit steigt ein Jahr nach dem Zuzug (No. 14/2023).

Kuwahara, Y. (n.d.). Migrant workers in the post-war history of Japan. Japan Labor Review, 25-47.

Lee, R., & Miller, T. (2000). Immigration, social security, and broader fiscal impacts. American Economic Review Papers & Proceedings, 90(2), 350-354.

Li Rosenberg, Q. (2024). The control and agency dialectic of guest worker programmes: Evidence from Chinese construction workers in Japan’s Technical Intern Training Program (TITP). Journal of Ethnic and Migration Studies, 50(16).

Lie, J. (2008). Zainichi (Koreans in Japan): Diasporic nationalism and postcolonial identity. University of California Press.

Liu, L. (2000). Public pension reform in Japan. Social Security Bulletin, 63(4), 99-106.

Liu-Farrer, G. (2023). The logics of staying for highly skilled Asian migrants in Japan. Asian and Pacific Migration Journal, 32(1).

Lu, Y. (2024). An Econometric Analysis of Non-enrollment in the National Pension by Foreign Residents in Japan (Keio-IES Discussion Paper 2024-027), Keio University. Tokyo.

Mahmood, T., & Schömann, K. (2003). The determinants of the migration decision of IT-graduates from Pakistan (WZB Discussion Paper FS IV 02-03a). WZB.

MHLW (Ministry of Health, Labour and Welfare). (2009). Outline of the public pension system in Japan.

MHLW (Ministry of Health, Labour and Welfare). (2009a). 平成１６年年金制度改正 ～年金の昔・今・未来を考える～.

MHLW (Ministry of Health, Labour and Welfare). (2009b). 第8章　日本の公的年金制度の概要.

MHLW (Ministry of Health, Labour and Welfare). (2009c). Chapter 12 Management of the Pension Reserve Fund.

MHLW (Ministry of Health, Labour and Welfare). (2009d). 第14章　企業年金・国民年金基金等私的年金概論.

Mientus, F. (2006). Zur Quantifizierung wiedervereinigungsinduzierter Kosten und Transfers in der Gesetzlichen Rentenversicherung. Mannheim: MEA.

Ministry of Health, Labour and Welfare (Japan). (n.d.). Social Security Agreements with Other Countries (Japan-Germany agreement).

Ministry of Health, Labour and Welfare (MHLW). (2011). Adopting a Macro-Economic Slide Formula (White Paper on Health, Labour and Welfare, English edition, pp. 1-2). Tokyo: MHLW.

Ministry of Health, Labour and Welfare (MHLW). (2019). Summaries of the 2019 Actuarial Valuation (English summary). Tokyo: MHLW.

Ministry of Health, Labour and Welfare, Pension Bureau. (n.d.). Pension Security: Outline of Pension System. Tokyo: MHLW.

Ministry of Health, Labour and Welfare, Pension Bureau. Adopting a Macro-Economic Slide Formula. (n.d.). [Slide].

Ministry of Health, Labour and Welfare. (2004, August). History, overview and status of public pension system in Japan (tentative translation). Office for Planning of International Pension Affairs.

Ministry of Health, Labour and Welfare. (2019). 2019（令和元）年財政検証結果レポート-「国民年金及び厚生年金に係る財政の現況及び見通し」（詳細版）第２章 国民年金・厚生年金の財政の現況

Ministry of Health, Labour and Welfare. (2024a). Overview of Pension System Revision

Ministry of Health, Labour and Welfare. (2024b). General Outline of Pension System

Ministry of Health, Labour and Welfare. (2025). Press release: Pension amounts for FY2025 (令和7年度の年金額改定についてお知らせします).

Ministry of Justice (Immigration Bureau) & Ministry of Health, Labour and Welfare (Human Resources Development Bureau). (2017, April). New Technical Intern Training Program (slide deck). Tokyo: Government of Japan.

Ministry of Justice. (2006). Registered foreigners by nationality, 1950-2006.

Ministry of Justice. (n.d.). Annual Report of Statistics on Legal Migrants.

Ministry of Justice, Japan. (n.d.). 帰化許可申請者数等の推移 [Trends in the number of naturalization applications, approvals, and disapprovals]. Retrieved February 23, 2026, from https://www.moj.go.jp/MINJI/toukei_t_minj03.html

Nagaya, Y., Gillin, N., & Smith, D. (2024). South-East Asian nurses’ experiences under the Economic Partnership Agreement (EPA) in Japan: How language ability affects self-confidence and interpersonal relationships. Journal of Transcultural Nursing, 35(6), 465-474.

National Institute of Population and Social Security Research. (2017). Population Projections for Japan (2017): 2016-2065. Appendix: Auxiliary Projections 2066-2115. Tokyo: IPSS.

National Institute of Population and Social Security Research. (2023). Population Projections for Japan (2021-2070).

National Tax Agency Japan. (n.d.). No.12005: Income tax on lump-sum withdrawal payments.

Nenkin (Japan Pension Service). Nenkin.go.jp. (2025). National Pension System.

OECD. (1973). OECD Economic Surveys: Japan 1973.

OECD. (1974). OECD Economic Surveys: Japan 1974.

OECD. (2004). Trends in International Migration: SOPEMI 2003 edition. Paris: OECD.

OECD. (2010). International Migration Outlook: SOPEMI 2010. Paris: OECD Publishing.

OECD. (2015). OECD Economic Surveys: Japan 2015. Paris: OECD Publishing.

OECD. (2016). OECD Economic Surveys: Germany 2016. Paris: OECD Publishing.

OECD. (2023). Pensions at a Glance 2023: Country Profile - Germany. Paris: OECD Publishing.

OECD. (2023). Pensions at a Glance 2023: OECD and G20 Indicators.

Okamoto, A. (2024). Pension Reform for an Aging Japan: Welfare and Demographic Dynamics. The SSRN Electronic Journal.

Okamoto, A. (2025). Pension reform for an aging Japan: Welfare and transition dynamics. Journal of the Japanese and International Economies.

Onuki, H. (2023). Informalization and temporary labor migration: Rethinking Japan’s Technical Intern Training Program from a denationalized perspective. Critical Sociology, 51(1).

OECD. (2024). International Migration Outlook 2024. Paris: OECD Publishing.

Organization for Technical Intern Training (OTIT). (2024). Overview of the Technical Intern Training Program. OTIT.

Promotion and Mutual Aid Corporation for Private Schools of Japan. (n.d.). “Lump-sum Withdrawal Payments to Non-Japanese Nationals.” https://www.pmac.shigaku.go.jp/en/pension/pension_08/index.html

Rosenberg, Q. L. (2024). The control and agency dialectic of guest worker programmes: Evidence from Chinese construction workers in Japan’s TITP. Journal of Ethnic and Migration Studies, 50(16), 4215-4233.

Roßbach, G. (2022). Change as the basis of a solid future: The pension reform of 1957, still distinctive after 65 years (DRV-Booklet, 1/2022).

Rowthorn, R. (2008). The fiscal impact of immigration on the advanced economies. Oxford Review of Economic Policy, 24(3), 560-580.

Sakamoto, J. (2005). Japan’s pension system-Evaluating the 2004 reform and establishing clear principles for further reforms (RIETI Discussion Paper). Tokyo: RIETI.

Sautter, U. (2004). Deutsche Geschichte seit 1815.

Schmähl, W. (1999). New developments and future directions of the public pension system in Germany. Bremen: Centre for Social Policy Research.

Sevak, P., & Schmidt, L. (2014). Immigrants and retirement resources. Soc. Sec. Bull., 74, 27.

Shimasawa, M., & Oguro, K. (2010). Impact of immigration on the Japanese economy: A multi-country simulation model. Journal of the Japanese and International Economies, 24(4).

Social Security Administration (SSA). (1973). Flexible retirement feature of German pension reform. Social Security Bulletin, 36(7).

Sozialbeirat. (2017, November 22). Gutachten des Sozialbeirats zum Rentenversicherungsbericht 2017. Berlin. https://www.sozialpolitik-aktuell.de/files/sozialpolitik-aktuell/_Politikfelder/Alter-Rente/Dokumente/2017_11_SozBei_Gutachten%20zum%20Rentenversicherungsbericht%202017.pdf

Specified Skilled Worker Support Site (Japan). (2024). Specified Skilled Worker (SSW) - System overview.

Statistics Bureau of Japan. (n.d.). Labour Force Survey-Historical data (Basic Tabulation), seasonally adjusted monthly series, 1953-1960.

Statistics Bureau, MIC (Japan). (2024). Statistical Handbook of Japan 2024.

Statistisches Bundesamt (Destatis). (2025). Migration und Integration: Einbürgerungen und ausgeschöpftes Einbürgerungspotential (Stand: 4. Juli 2025). Retrieved February 23, 2026, from https://www.destatis.de/DE/Themen/Gesellschaft-Umwelt/Bevoelkerung/Migration-Integration/Tabellen/einbuergerungen-einbuergerungsquote-lr.html

Steffen, J. (2002, October). Die Anpassung der Renten in der Rentenversicherung der Arbeiter und Angestellten: Von der Rentenreform 1957 bis zum AVmEG [Manuscript]. Institut Arbeit und Wirtschaft, Bremen.

Stokes, L. (2019). The permanent refugee crisis in the Federal Republic of Germany, 1949-. Central European History, 52(1).

Takayama, N. (2003). The Japanese public pension system: What went wrong and what reform measures we have. Paper presented at “Japan and Italy: Economic Performances and Policies Compared,” Bocconi University, Milan, 9-10 October 2003.

TNS Infratest Sozialforschung. (2015). Verbreitung der Altersvorsorge 2015 (AV 2015): Methodenbericht. Bonn: Deutsche Rentenversicherung.

Tsuda, T. (1999). The permanence of “temporary” migration: The “structural embeddedness” of Japanese-Brazilian immigrant workers in Japan. The Journal of Asian Studies, 58(3).

Tsuda, T. (2008). Local citizenship and foreign workers in Japan. The Asia-Pacific Journal | Japan Focus, 6(5), 2762.

Tsuda, T. (2010). Ethnic return migration and the nation-state: Encouraging the diaspora to return “home.” Nations and Nationalism, 16(4), 616-636.

United Nations, Department of Economic and Social Affairs (UNDESA), Population Division. (2020). International Migrant Stock 2020.

United Nations, Department of Economic and Social Affairs, Population Division. (2024). International Migrant Stock 2024: Key facts and figures.

United Nations. (2002). World population ageing: 1950-2050. Department of Economic and Social Affairs, Population Division.

von Koppenfels, A. K. (1999). Citizenship and participation in post-Cold War Germany: Aussiedler migration as a challenge to German citizenship (Doctoral dissertation, Georgetown University).

Weber, J. (2025). Freizügigkeitsmonitoring: Migration von nicht-deutschen Unionsbürgerinnen und -bürgern nach Deutschland. Jahresbericht 2024. Nürnberg: Bundesamt für Migration und Flüchtlinge (BAMF), Forschungszentrum.

Yasuda, Y. (2022). Can they call Japan home? Japanese nationalism and unskilled labour immigrants. Excursions, 12(1), 24-37.