Schmid Comparative Migration Studies (2020) 8:25 https://doi.org/10.1186/s40878-020-00182-5 ORIGINAL ARTICLE Open Access The architecture of national boundary regimes: mapping immigration and citizenship policies in 23 democracies 1980–2010 Samuel D. Schmid1,2 Correspondence: schmid@mmg. mpg.de 1 Max Planck Institute for the Study of Religious and Ethnic Diversity, Göttingen, Germany 2 European University Institute, Florence, Italy Abstract In this article, I introduce a typology that maps the regulation of two fundamental boundaries of modern nation-states regarding immigration: territorial boundaries and membership boundaries. Based on a theory of the structural logics underlying Immigration Regime Openness (IRO) and Citizenship Regime Inclusiveness (CRI), I make four observations on the two-dimensional policy space determined by the relative porousness of these two boundaries. First, a Categorical Principal Component Analysis (CATPCA) using a combination of original and existing panel data across 23 liberal democracies from 1980 to 2010 confirms that IRO and CRI are internally consistent and statistically distinct dimensions. Immigration policies therefore appear more coherent than often assumed. Second, the distribution of cases over the four ideal-typical policy configurations from 1980 to 2010 shows that more and more cases combine relatively liberal immigration policies with relatively liberal citizenship policies. Behind this finding are, third, overall liberalizing trajectories in both policies as well as a pattern of convergence in immigration policies. The liberalisation of immigration policies is most notable until 1996 and the level of openness fluctuates thereafter. Regarding citizenship, I provide evidence for a much-cited restrictive turn during the 2000s. In addition, I show that there has already been a restrictive turn in citizenship during the 1990s. Fourth, instead of the trade-off anticipated by much of the literature, I find an increasingly positive correlation between IRO and CRI. The new typology, its underlying theory, and the subsequent findings significantly advance our understanding of the most fundamental boundaries of modern nation-states. Keywords: Immigration policies, Citizenship policies, Typology, Principal component analysis, Policy trends Introduction Immigration-related policies can be conceptualised along two basic dimensions. On the one hand, territorial boundaries are about immigration policy and refer to territorial admission and the granting of (long-term) legal residence. On the other hand, membership boundaries are about immigrant policy and refer to the treatment of © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.