In this article, the author introduces 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), the author makes 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, the author provides evidence for a much-cited restrictive turn during the 2000s. In addition, the author shows 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, the author finds 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.

Sam Schmid, The architecture of national boundary regimes: mapping immigration and citizenship policies in 23 democracies 1980–2010, Comparative Migration Studies, 2020.