Historically, citizenship has been a gatekeeper to political and social rights within communities, as entitlements of membership were closely connected to gender, race, and class. Nowadays, citizenship is a symbol of equality within states as much as a marker of inequality among states. It is (1) a defining feature of the international state system, which both reflects and reinforces inequalities of wealth and opportunity around the world, and (2) a tool for social closure, through which states determine who belongs to the group that can share common entitlements and who, by contrast, are excluded from them. These two characteristics of citizenship are central to understanding the citizenship-migration nexus: whereas the promise of equality represents a strong driver for migrants to acquire citizenship in their destination states, the different opportunities attached to citizenship of different countries encourage migration of individuals from less privileged parts of the world and enable mobility for those with a citizenship status in the more advantageous countries.

This chapter aims to unpack the linkages between citizenship and migration by exploring the various ways in which citizenship status is crucial to migration opportunities, as well as how, in turn, the acquisition and loss of citizenship have been affected by modern migratory flows. After clarifying the key concept of citizenship and reviewing relevant theories, we highlight conflicting trends that have contributed to both the devaluation and the revaluation of citizenship, including (a) the resilience of national sovereignty in the context of regional and international norms; (b) the tension between the preservation of cultural identities of states and economic benefits of migration; and (c) the diversification of migration and dual citizenship acceptance. We then introduce some key studies and end with pointers for further study.

1 Concepts and Theories

1.1 What Is Citizenship?

Citizenship is a central concept in the practice and study of politics, ever since the times when Aristotle spoke of self-rule as the key element of participating in democratic governance and thus of “being a citizen” (Morrison, 1999). Yet as a result of a plethora of different views on what “being a citizen” precisely is (and what it is not), citizenship is often viewed as one of those “essentially contested concepts” (Cohen & Ghosh, 2019). For some, citizenship is simply a legal status that comes together with a set of rights; for others, citizenship goes much beyond a ‘mere’ status and is only realised in practice by active participation in the polity or requires a form of shared identity.

In the literature on citizenship and migration, most scholars align their understanding of the concept with the way in which citizenship is typically used in international law, i.e. as a legal status that entitles a person to a set of rights and comes with set of obligations, such as taxation or jury duty, while recognising that both the access to the status and the mix of rights and obligations have historically varied within and between polities.

Citizenship is a legal status, which articulates the relationship between an individual and a state and designates legal entitlements and obligations to parties in that relationship.

In this relational understanding, ‘citizenship’ is synonymous with ‘nationality’ and denotes either of the two uses of the concept in domestic legislation, e.g., citizenship in the US or nationalité in France. To make things more complicated, while these two terms are synonymous in some countries, they denote different things in others. For instance, the British Nationality Act defines, among other things, British citizenship. In Latin America, ‘nationality’ commonly refers to a legal status, and ‘citizenship’ to political membership entailing rights and duties (e.g., voting rights, military duty) that can be exercised only upon reaching the age of majority and may be lost upon emigration.

1.2 Citizenship and Migration: How Do They Relate?

In this chapter, we refer to migration as international migration. Following the definition of the IOM, the International Organization for Migration, we understand migration as the movement of a person away from their place of usual residence across an international border, temporarily or permanently, and for a variety of reasons. This definition refers both to immigration (which takes a destination country perspective) and to emigration (taking an origin country perspective).

Citizenship and migration have a mutually constitutive relationship in two crucial ways. On the one hand, citizenship status is crucial to migration opportunities, both as a status that can facilitate and restrict individual mobility, as well as a driver of mobility aspirations. On the other hand, political and economic contestation over migration—be it immigration or emigration—affect the regulation of citizenship.

1.2.1 How Citizenship Affects Migration

Until the end of the Second World War, citizenship did not entail an across-the-board equality status, but was rather a contrivance for membership hierarchies within polities. With the modern understanding of the pivotal role of citizenship within the international state system where each person should be a citizen of at least one state, i.e. everyone should have “the right to have rights” (Arendt, 1951, p. 294), the notion became—at least discursively—associated with a guarantee of equality of civic, political and social rights inside the states’ borders. Even so, there is great variation in how states allocate membership entitlements; what opportunities they provide to those holding the legal status of citizenship; and how they constitute identities, ideas and actions engrained in it. In other words, while all citizens of a state are (presumably) equal, some citizenships are less equal than others. This global inequality of citizenship is a key driver of migration—in the form of economic migration, or population flows caused by conflict or environmental disaster.

1.2.2 How Migration Affects Citizenship

Migration has an impact on how states regulate the access to and loss of citizenship, as well as the associated privileges of citizens. This is best illustrated by the rules that govern citizenship at birth, as well as in rules for residence-based naturalisation, special naturalisation or conditions under which citizenship can be lost.

Most of the world’s population automatically receive citizenship at birth (attribution), on the basis of descent or birth within a country’s territory. The granting of citizenship on the basis of citizenship of a person’s parents reflects the ius sanguinis (the right of the blood) principle for citizenship acquisition. By contrast, the granting of citizenship as a result of having been born in a particular country indicates the ius soli (the right of the soil) principle for obtaining citizenship. The territorial principle is typically found in classic settler states, such as those in North and South America, where ius soli was seen as the best way to assert independence vis-à-vis former colonial powers by ensuring that all newly born where citizens of the new republics rather than colonial subjects (Acosta, 2016). By contrast, in European ‘sending’ countries, the prevalence of descent-based transmission of citizenship reflects -at least partly- a political will to ‘hold on’ to the diaspora. This, for instance, is why Argentinians of Italian descent still have access to Italian citizenship, even after many generations.

We should, however, avoid two common misunderstandings. First, while the attribution of citizenship at birth through ius soli is typically referred to as ‘birthright citizenship’ in the North American context, both descent-based and territory-based principles are founded on birthright (Honohan & Rougier, 2018). Second, whereas countries are often categorised (including by scholars) as either ius soli or ius sanguinis countries, in practice, most countries operate a mixture of both principles. For example, children born abroad to US citizens can, under certain conditions, also acquire US citizenship through descent (but—although this interpretation is controversial and not fully settled—are no longer considered ‘natural born’ citizens and thus are not eligible to be President). Furthermore, in most countries where descent is the main basis for citizenship attribution, children born on the territory who would otherwise be stateless (such as foundlings) are also considered citizens and, in some cases, children born to non-citizens can also have a claim to citizenship.

Other than by birth, citizenship can result from naturalisation upon migrating and settling in another country (Bloemraad, 2006; Yang, 1994), or through a real or presumed entitlement without relocating to a destination state (Harpaz, 2019). In the first case, the acquisition of an alternative or additional citizenship, is a consequence of migration, and is subject to the establishment of a connection with the destination state through multiannual residence, but also other conditions, such as language knowledge, socialisation, good character, etc. In the second, it often takes place without migration, and instead reflects a strategic decision of an individual to enhance her lifetime opportunities by holding the legal status of citizenship in more than a single state.

Finally, migration can result in loss of citizenship, either by voluntary renunciation (such as by US citizens residing abroad who no longer wish to be taxed under the Foreign Account Tax Compliance Act, or FATCA) or involuntarily as a result of the acquisition of another citizenship, residing abroad, or due to security or other concerns about allegiance or ties to another nation.

2 Theories of Citizenship

Theories of citizenship can be normative or empirical. The normative ones address questions about who should be a citizen and thus should have the related rights; the empirical ones ask why states regulate citizenship in certain ways and why individual migrants take up citizenship or not.

2.1 Normative Theories

Normative theories of citizenship deal with two key questions: (1) whom should polities include and exclude as members, and (2) what the substance of citizenship should be. While the core controversies related to these questions are likely to persist in theory and in practice, understanding the different elements of this debate helps us to grasp the key dilemmas that policymakers face when deciding about migration control and access to citizenship.

Normative political theorists address the first question by looking at the outer rims of the demos, and discuss the so-called “boundary problem” (see Bauböck, 2017 for an overview of this discussion). This problem, in its essence, is that when deciding on who can be a citizen (and thus participate in decision-making), democracies do not include those who do not, at that time, take part in the deliberative process. For example, a country may hold a referendum on whether to attribute citizenship by ius soli to children of immigrants born in the country, but neither of those affected by this decision—immigrants and their children—will take part in this referendum. Theoretical positions on how to deal with this problem are manifold. Robert Dahl (1989, p. 120) argues that the demos should be constituted by “all adults subject to the binding collective decisions of the association”. Robert Goodin (2007) embraces a far more inclusive approach, pointing out that if immigration rules affect potential migrants they should have a say as well, while Rainer Bauböck (2017) would equalise the demos to “stakeholders”, including “those and only those whose autonomy and well-being depend on the collective self-government and flourishing of a particular polity”.

Normative debates on the substance and meaning of citizenship are equally diverse. They presume alternative conceptions of citizenship-as-desirable-activity and citizenship-as-a-legal-status (Kymlicka & Norman, 2000). Whereas in the first (republican) ‘thick’ conception citizenship is a function of one’s participation in the polity, in the ‘thin’ conception (liberal), no such active role is required from the citizen in order to be considered a full member of the political community. Further to this, Will Kymlicka’s (1995) notion of “multicultural citizenship” includes group-differentiated rights for cultural minorities, such as language or education.

The different conceptions of citizenship offer a different response to the question of whether there should be special group rights for immigrants. From the perspective of liberalism, Christian Joppke (2001) claims that immigrants have “waived” their societal culture and thus should not be granted special rights. A more participatory normative stand would argue that when a receiving country voluntarily admits immigrants, it should acknowledge their cultural specificities and not deny special rights ex ante (Parekh, 1997). Kymlicka (1995) emphasised that through the lenses of his “multicultural citizenship”, voluntary migrants cannot be granted the same rights as cultural minorities, but that this normative stance is less clear in cases of forced migration.

2.2 Empirical Theories

2.2.1 Citizenship Regime Theory

There is longstanding multidisciplinary tradition of studying citizenship regimes, both comparatively and in case-oriented area studies. Citizenship regimes may be understood as institutionalised systems of formal and informal norms that define access to legal status, as well as rights and duties associated with that status, within a polity (Vink, 2017). Research in this field is focused on both descriptive and explanatory research questions.

Descriptive research questions such as, what differentiates one citizenship regime from another and how to classify the different models for governing citizenship, produce typologies of citizenship regimes. For instance, we often talk about ‘inclusive’ or ‘restrictive’ citizenship policies, suggesting that there is a single dimension of ‘inclusiveness’ underlying citizenship policies. These are typically measured, for example in the Migrant Integration Policy Index (MIPEX) indicator on ‘Access to Nationality’, by residence requirements for naturalisation, dual citizenship acceptance, as well as the presence of civic knowledge and language requirements, as visualised in Fig. 22.1 (Schmid, 2021 for an alternative Citizenship Regime Inclusiveness Index). However, we should keep in mind that citizenship policies serve not only to include (or exclude) of immigrant populations resident on the territory, but also to maintain a legal link with citizens and their descendants who have left the territory of a state. Using GLOBALCIT’s Citizenship Law Indicators, Vink & Bauböck (2013) demonstrate that citizenship policies in Europe vary: they can prioritise ethnocultural inclusiveness over the territorial one, or, vice versa, be inclusive towards immigrants and emigrants (‘expansive’ regimes), or restrictive towards both (‘insular’ regimes).

Fig. 22.1
A stacked bar graph for the relative inclusiveness of policies on access to citizenship in Europe. With four inclusive policies, Sweden and Ireland received the highest scores.

The relative inclusiveness of policies on access to citizenship in Europe (Source: https://migrationresearch.com/migration-policy-indicators). Higher scores indicate more inclusive policies

Explanatory research focuses on the determinants of variation in regimes: why are some regimes more inclusive, at some point in time, towards specific groups, and why are other regimes (or the same regime, at a different point in time) more exclusive, towards specific groups? Much of the work in this field is rooted in historical institutionalism, a social science approach that emphasises the path-dependent nature of institutions, such as citizenship. This is a logical approach given that citizenship is closely related to political self-determination and inherently linked to the political development of states. In his seminal work, Brubaker (1992) compared the development of citizenship regimes in France and Germany and linked these to different conceptions of nationhood in both countries. Comparative social scientists such as Howard (2009), Janoski (2010), and Joppke (2003) have also drawn on explanatory factors such as colonial history, the relative size of the immigrant population, political composition of the government, and the relative strength of right-wing populist parties. Finally, scholars of international diffusion (Checkel, 1999; Vink et al., 2019) have pointed out that we should be careful in explaining trends within countries by only looking at country-specific factors. After all, even if citizenship is nationally regulated, policies may still be affected by non-binding regional or even global norms that push developments in many countries in a similar direction (see also related work on diaspora institutions by Gamlen (2014) and Turcu & Urbatsch (2015)).

2.2.2 Theories of Citizenship and (Im)mobility

The international state system is divided into populations and territories disparate in terms of resources and wealth, whereas individuals are on the lookout for opportunities and environments where they can make the best use of their abilities and skills. Discussing how income inequalities depend on circumstances beyond individual control, Branko Milanović (2011, p. 142) highlighted that

[o]ne’s income thus crucially depends on citizenship, which in turn means (in a world of rather low international migration) place of birth. All people born in rich countries thus receive a location premium or a location rent; all those born in poor countries get a location penalty.

Economic migration takes place when individuals leave their countries of origin to settle in countries or regions that can offer them a more prosperous life course. While there are different kinds of economic migrants, their decision to relocate has commonly been a reflection of wealth inequalities existing across and within countries (de Haas, 2010; Hagen-Zanker, 2008). The former determine the direction of migration (where from—where to), while the latter influence its size and character (who will migrate and why). Equally, for those fleeing wars, instability or environmental disasters, citizenship of origin, received through the fact of birth is the most likely determinant of opportunities, and thus a push factor for migration.

2.2.3 Theories of Citizenship Acquisition

Why do some immigrants, in some destination countries, acquire citizenship, whereas others do not? The dominant theoretical perspective in this strand of literature is an economic one, viewing the acquisition of destination country citizenship by migrants as the result of a cost-benefit calculation (Yang, 1994; DeVoretz & Irastorza, 2017). In other words, immigrants weigh up the benefits of naturalisation against the costs of acquiring citizenship, such as having to give up one’s origin citizenship or having to pay what amounts to a substantial fee in some countries (e.g. in the UK this costs nearly 1500 euro for a single naturalisation application, whereas in Sweden it costs only around 150 euro and stateless persons and refugees are exempted). From an economic perspective, the marginal ‘added value’ of destination country citizenship vis-à-vis origin country citizenship plays a large part in migrants’ utility calculations. Hence, using the human development of countries as a proxy for the value of citizenship, scholars have observed that migrants from less developed and unstable parts of the world are more likely to naturalise in highly developed countries (Vink et al., 2013). Migrants who can retain citizenship of their country of origin are also more likely to naturalize, since they do not need to make a trade-off at all (Jones-Correa, 2001). The high naturalisation rates of British nationals in countries of the European Union (EU) in the context of Brexit (the UK’s exit from the EU) also fits in this economic perspective, as British nationals aim to ensure their free movement rights within the EU by naturalising abroad (Auer & Tetlow, 2020).

Alternative theoretical perspectives point for example to the importance of political promotion of citizenship and bureaucratic practice (Bloemraad, 2006; Huddleston, 2020) or the relevance of the family context (Street, 2014; Helgertz & Bevelander, 2017; Peters et al., 2016). These studies demonstrate that utility calculations certainly matter for immigrant naturalisation but need to be understood in a broader political and sociological context.

3 Trends and Patterns

Three conflicting trends have contributed to both the devaluation and the revaluation of citizenship in the context of global mobility: (a) the resilience of national sovereignty in the context of regional and international norms; (b) the tension between the preservation of cultural identities of states and economic benefits of migration; and (c) the diversification of migration and dual citizenship acceptance.

3.1 National Sovereignty, Regional and Global Norms

The basic premise of the current international system is that controlling borders and access to citizenship is a national competence. However, this competence is exercised within an ever-denser system of regional and global norms (e.g., non-discrimination, gender equality, prevention of statelessness), which inevitably question the core conception of citizenship as an ‘exclusive domain’ of the state. An example would be the 1957 Convention on the Nationality of Married Women, which marked a significant step towards eliminating gender discrimination in nationality law with provisions preventing the automatic loss and acquisition of the husband’s citizenship upon marriage (Bredbenner, 2018). A further example are the regional integration processes, including the EU, the Nordic Council, and the Southern Common Market in Latin America (Mercosur). In addition to offering free movement and residence rights to citizens of the respective Member States thus enabling migration, these regional organisations have also had an impact on citizenship regulation. While the rules of acquisition and loss of citizenship are ultimately decided by individual Member States of the EU, judgments of the Court of Justice (CJEU) related to EU Citizenship (a status that offers additional rights to Member States’ citizens, but does not substitute their national citizenship), such as Rottmann and Tjebbes, resulted in safeguards from automatic loss of nationality. The effects of regional processes on citizenship are also reflected in legal provisions that facilitate acquisition of citizenship for individuals holding a nationality of one of the members of a regional organisation. This is the case, for instance, in the Nordic countries whose citizens can naturalise after 2 years in another Nordic state, while other immigrants remain subject to residence periods between 5 (in Finland and Sweden) and 9 (in Denmark) years.

3.2 Economic Opening, Political Closing

International migration is driven to a large extent by push-pull factors. On the destination side: strong ‘pull’ by business for labour inflow, both unskilled and skilled. On the origin side: this leads to concerns about brain drain. Generally, it is recognised that in order to optimise payoffs from migration at a global level we need not only migration systems that provide opportunities for migrants to settle in destination countries (i.e. citizenship), but also flexible migration schemes that allow for circular migration. However, there are also counterforces from labour unions and electoral pressures that lead to stricter migration controls and restrictive access to citizenship (Freeman, 1995).

As a result, democracies are trapped in a “liberal paradox” that manifests itself in a tension between open borders and inclusive citizenship (Hollifield, 1992, 2004; but see Schmid, 2020 for a critique). To maximise material welfare in a globalising world, transnational economic forces propel liberal states toward greater openness for migrants (Hollifield, 2004). At the same time, political forces push for greater territorial closure in order to ensure security, preserve the democratic social contract, and to protect the cultural cohesion of the national community. So-called civic integration programmes representing a cultural turn reflect a tension between the socio-economic needs of states and their attempts to preserve the dominant culture.

3.3 Diversified Migration, Multiple Citizenship

International migration has changed and diversified over the last century, mostly as a result of a shift in the directionality of human movement. A handful of “prime destination countries” host migrants from a broad range of developing states (Czaika & De Haas, 2014) a trend that has transformed some traditionally ‘sending’ countries such as Italy or Ireland, into ‘receiving’ countries for migrants. The new states of origin thus face pressures from remittance-sending emigrants to tolerate dual citizenship (Vink et al., 2019; Leblang, 2017). The traditional ‘sending’ states that have become countries of immigration seek out strategies to balance between increased diversity inside their borders and preservation of national and cultural identities beyond them. As a result of these developments and human rights norms discussed above, an increasing number of states have become tolerant of dual nationality for emigrants since the 1960s (Vink et al., 2015) (Fig. 22.2).

Fig. 22.2
A line graph for expatriate dual citizenship acceptance. In 2020, the lines for Oceania, America, Europe, the world, Africa, and Asia reached 93%, 91%, 80%, 76%, 70%, and 65%, respectively.

Expatriate dual citizenship acceptance around the world, 1960-2020 (Source: https://macimide.maastrichtuniversity.nl/dual-cit-database/)

This particular trend has, in turn, reconstituted the function and value of citizenship for individuals as the ‘holders’ of this status and associated rights as well as for states as the sole ‘givers’ of it. For individuals, citizenship of the country of origin no longer represents the primary mechanism of ensuring political participation and social rights; this function is now performed by the legal status they possess in the destination state. The latter determines the extent of their political membership in the country where they have settled and where they, and presumably, their descendants hold stakes. Thus, holding on to the citizenship of the country of emigration has gained a largely symbolic function as a link to family, culture, or as representative of ethno-national identity (Lindholm, 2020). For states of emigration, the reciprocal function of citizenship has diminished as political and social rights are increasingly dependent on the combination of citizenship and residence (Spiro, 2012). For states of immigration, tolerance of dual citizenship is a mechanism for fostering integration and cultural pluralism. The costs of tolerating such dual citizenship are low, while benefits may come in the form of loyalty and integration in receiving states, or in the form of reinforcing kinship and economic gains from the diaspora in the states of origin (Leblang, 2017; Naujoks, 2013). Hence there is a gradual shift from the idea of citizenship as a singular relationship between individuals and states to an acceptance of “plural allegiance” (Aleinikoff & Klusmeyer, 2011; Sejersen, 2008; Spiro, 1997).

4 Key Topics

4.1 Strategic Citizenship

While it is true that citizenship both provides and constrains migration opportunities, it can equally be an enabling factor for non-migration mobilities, and strategic and instrumental acquisition of passports (Harpaz, 2019; Joppke, 2019). This practice has become widespread in view of the pervasive globalisation and the growth in dual citizenship tolerance. Strategic citizenship refers to an additional legal status of citizenship, which serves an instrumental function for the individual in that it compensates for the shortcomings of legal status in the country of origin, commonly in terms of travel and settlement. Harpaz (2019, pp. 11–12) identifies six strategies for acquiring a compensatory second citizenship, including ancestry, kinship, strategic cross-border birth, investment, marriage, and residence. These will have different outcomes as enabling factors for migration. In cases of citizenship acquisition on the basis of residence, marriage, or cross-border birth, the person will normally have already moved to another country. By contrast, in instances of citizenship acquisitions through real or presumed ancestry or kinship, or on the basis of investment, migration and settlement in the destination country need not have taken place and may as well never happen. Acquisitions of passport through ancestry characteristic of emigrant countries (Italy, Spain), those based on remedial rights for descendants (Germany, Portugal Spain), or presumed co-ethnicity in view of broader nation-building projects or foreign policy objectives (Croatia, Hungary, Romania, Russia) are commonly used as an entry ticket to broader opportunities that they provide. For example, a descendant of a Sephardic Jew expelled from the Iberian Peninsula in the fifteen century may acquire a Spanish or Portuguese passport not exclusively to migrate to Spain or Portugal. Rather, they may use such passport to gain access to the rights of EU citizenship and thus the possibility to settle in any of the other 26 Member States. A wealthy person, who obtains a passport on the basis of investment will commonly remain a “long-distance citizen” (Džankić, 2019) and capitalise on the mobility and tax benefits of the second passport, rather than settling in the country of their strategic nationality. In other words, strategic citizenship acquisitions can be an outcome of migration (e.g., in cases of marriage), pull factors for some migrants (e.g., ancestry) or enablers of global mobility rather than settlement (e.g., investors).

4.2 Citizenship: Crown or Catalyst?

Does citizenship matter for the life experiences of immigrants? Few would contest that it does, because citizenship provides residence security and protection from expulsion (Bloemraad, 2017). But does citizenship still have an added value for immigrants who have secured permanent residence rights in a country or is it a hollow promise of integration in the destination country?

The research agenda on this question is both inspired by and aims to inform debates among politicians who decide about the conditions under which citizenship should be accessible to immigrants. Those on the ideological right of the political spectrum argue that citizenship should be available only under strict conditions and only for immigrants who have demonstrated—by residing in a country a very long period, by actively participating in social life, by being economically successful—that they are ‘well integrated’ in society. From this viewpoint, citizenship becomes a reward for good integration. By contrast, those on the ideological left maintain that citizenship is a necessary condition for good integration and therefore should be accessible to immigrants under reasonable conditions—after a short residence period and with few additional requirements. In this view, naturalisation is seen as a catalyst for integration, something that encourages and spurs on increased participation in society.

Due to the ideological controversy, naturalization policies frequently reflect electoral trends within countries (Howard, 2009). Scholars inform these debates by looking at whether assumptions of one or the other position are more likely to happen in practice. For instance, to test the empirical assumption underlying the ‘catalyst’ perspective, researchers would look at whether there is causal effect of citizenship acquisition on immigrant integration outcomes, such as having paid employment, higher income, participating in social life, being well-informed about current developments, and having a sense of belonging to the country.

However, there is a chicken-and-egg problem here: if naturalised immigrants are better integrated (measured according to some of the indicators listed above) is this because citizenship acquisition was a catalyst for their integration, or were they already better integrated and therefore more likely to naturalise? In the quantitative literature on the so-called “citizenship premium”, two strategies have been developed to deal with this problem: a longitudinal approach and a quasi-experimental approach.

The longitudinal approach (building on the work by Bratsberg et al., 2002) follows integration outcomes (e.g., wages) over time for individual migrants and assesses whether outcomes are better after naturalisation, compared to before (i.e. whether there is wage growth). The findings from studies that apply this method indicate that, overall, migrants’ wages increase after they acquire citizenship, especially among migrants who have the highest risk to face difficulties on the labour market (Liebig & Von Haaren, 2011; Steinhardt, 2012; Peters et al., 2018, 2019).

The quasi-experimental approach has been developed especially in the context of the Swiss case, where until some years ago Swiss municipalities used referendums to decide on naturalisation applications of immigrants. By comparing otherwise similar immigrants who all applied for Swiss citizenship but either narrowly won or lost their naturalisation referendums, scholars demonstrated that receiving Swiss citizenship strongly improved long-term social integration (i.e. plan to stay in Switzerland, be an active member of clubs or associations), and led to substantial annual income increases, again, especially among more marginalised immigrant groups (Hainmueller et al., 2017).

Overall, while it is difficult to measure whether citizenship matters, creative approaches have been developed in the literature and most findings support the policy paradigm arguing that naturalisation is a catalyst for improving the social integration of immigrants rather than merely the crown on a completed integration process (Fig. 22.3).

Fig. 22.3
A screenshot mentions the data sources and recommendations for further reading. The subheadings include global citizenship observatory, N C C R, I S I, I O M, and Eurostat.

Suggestions for further reading and online sources