Schmid Comparative Migration Studies (2020) 8:25 Based on a much larger number of observations than is typically employed, the analysis presented here supports the alternative view that the most important policy components of citizenship regimes regarding ordinary immigration – residence duration requirements, multiple citizenship toleration, the strength of jus soli, as well as further naturalisation requirements (language tests, citizenship tests, and economic and criminal record conditions) – can be reduced to the same dimension of CRI. While the differentiation of civic integration as a separate dimension may be important in conceptual terms, and useful for specific analytical purposes, this analysis thus suggests that this aspect can also be incorporated into a one-dimensional statistical measure of citizenship regimes, more comprehensively understood. This supports the view that liberal-democratic concerns (or illiberal ones) and inclusive conceptions of nationhood (or exclusive ones) go together in structuring coherent citizenship regimes, though the various policy components cannot be neatly aligned with these two underpinning structures. Configurational analysis How do the observations configure in the two-dimensional space defined by IRO and CRI? Figure 2 presents the empirical distribution of all country-year combinations, both for the whole observation period (on the very right) as well as broken down by three geopolitical periods, which roughly correspond to the three decades from 1980 to 2010. Overall, most cases have relatively open immigration regimes and inclusive citizenship regimes (Fig. 2; 30% of observations). Regimes with this liberal cosmopolitan quality have become much more frequent over time. They were least frequent during the last decade of the Cold War (1980–1991), but in the most recent observation period (2002–2010) they make up almost half of all observations (46%). Fig. 2 National boundary regimes over time: ideal-typical empirical distribution. Bars indicate percentages; the categorisation is made according to whether an observation is above or below the arithmetic mean of IRO and CRI, respectively; Cold War period 1980–1991; Post 9/11 period 2002–2010; total period 1980–2010; N = 713 country-year observations Page 14 of 20

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