Comparative Report Dual Citizenship in the European Union: trends and analysis (2010-2020) Luuk van der Baaren1 1. Introduction Over the last few decades, attitudes towards dual citizenship have undergone a remarkable change. The Macimide Global Expatriate Dual Citizenship Database has shown that the share of countries where citizenship is automatically lost upon acquisition of another citizenship fell from 63% in 1960 to 24% in 2020.2 The increasing tolerance of dual citizenship is also starkly illustrated by the fate of the 1963 Strasbourg Convention on the Reduction of Cases of Multiple Nationality and on Military Obligations in Cases of Multiple Nationality. At its zenith, ten states were a party to the Second Chapter of the Convention, which imposed restrictions on dual citizenship between the signatory states. By 2020, only Austria and the Netherlands have remained.3 An extensive academic debate has unfolded on the drivers of the shift towards acceptance of dual citizenship, including but not limited to the indirect effects of gender equality, migratory movements, the prevalence of remittances and diasporic political pressure as well as international policy diffusion.4 1 Luuk van der Baaren is a postdoctoral researcher at the Globalcit Observatory, Robert Schuman Centre for Advanced Studies, European University Institute. He obtained his PhD degrees in Law from the University of Liège and Maastricht University. The author thanks Prof. Dr. Maarten Vink and Prof. Dr. Rainer Bauböck for their valuable feedback on an earlier draft of this report. 2 Vink, M., De Groot, G.R., Luk, N.C., MACIMIDE Global Expatriate Dual Citizenship Dataset, Harvard Dataverse, version 5, 2020, via < https://dataverse.harvard.edu/dataset.xhtml?persistentId=doi:10.7910/DVN/TTMZ08>, last accessed on 20 June 2020. 3 <https://www.coe.int/en/web/conventions/full-list/-/conventions/treaty/043/signatures>, last accessed on 20 June 2020. 4 Alarian, H. and Wallace Goodman, S., ‘Dual citizenship allowance and migration flow: an origin story’, Comparative Political Studies, Vol. 50 No. 1, 2017; Faist, T., Gerdes, J. and Rieple, B., ‘Dual Citizenship as a Path-Dependent Process’, International Migration Review, Vol. 38, No. 3, 2004; Faist, T., ‘The fixed and porous boundaries of dual citizenship’, in: Faist, T., Dual citizenship in Europe: From nationhood to societal integration, Farnham: Ashgate Publishing, 2007; Leblang, D. et al., ‘Harnessing the diaspora: dual citizenship, migrant return remittances’, Comparative Political Studies, Vol. 50 No. 1, 2017.; Martin, D., ‘The trend towards dual nationality’, in: Martin, D. and Hailbronner, K. (eds.), Rights and duties of dual nationals, The Hague: Kluwer, 2003; Mirilovic, N., ‘Regime type, international migration, and the politics of dual citizenship toleration’, International Political Science Review, Vol. 36, No. 5, 2014; Vink, M., and De Groot, G.R., ‘Citizenship attribution in Western Europe: International framework and domestic trends’, Journal of Ethnic and Migration Studies, Vol. 36 No. 5, 2010; Vink, M., Prokic-Breuer, T., and Dronkers, J., ‘Immigrant naturalisation in the context of institutional diversity: policy matters, but to whom?���, International Migration, Vol. 51 No. 5, 2013; Vink, M., Schakel, A., Reichel, D., Luk, C., De Groot, G.R., ‘The international diffusion of expatriate dual citizenship’, Migration Studies, Vol. 7 No. 3, 2019. RSCAS/GLOBALCIT-Comp. 2020/4 - © 2020 Author 1