From causes to consequences: Investigating the effects of differentiated integration on citizens’ EU support
| Author | Ioannis Vergioglou,Sven Hegewald |
| DOI | http://doi.org/10.1177/14651165221135742 |
| Published date | 01 March 2023 |
| Date | 01 March 2023 |
| Subject Matter | Articles |
From causes to
consequences: Investigating
the effects of differentiated
integration on citizens’EU
support
Ioannis Vergioglou
Center for Comparative and International Studies, ETH Zurich,
Zurich, Switzerland
Sven Hegewald
Center for Comparative and International Studies, ETH Zurich,
Zurich, Switzerland
Abstract
Research on differentiated integration has paid considerable attention to its causes.
However, we know very little about its consequences. Using the synthetic control
method and interactive factor models, this article investigates the effects of differen-
tiated integration on citizens’support for the EU. We find that in cases where member
states are granted an opt-out or are allowed to integrate into a policy area they were
previously excluded from, support increases. In contrast, support decreases when mem-
ber states are not granted a requested opt-out or are excluded from a policy area they
would like to join. These findings carry important implications for the EU’s legitimacy.
While differentiated integration has the potential to enhance citizens’legitimacy percep-
tions, it can also undermine them simultaneously.
Keywords
Differentiated integration, EU support, synthetic control method, two-way fixed effects
Corresponding author:
Ioannis Vergioglou, Center for Comparative and International Studies, ETH Zurich, Haldeneggsteig 4, Zurich,
8092, Switzerland.
Email: vioannis@ethz.ch
Article
European Union Politics
2023, Vol. 24(1) 206–224
© The Author(s) 2022
Article reuse guidelines:
sagepub.com/journals-permissions
DOI: 10.1177/14651165221135742
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Introduction
In its early days, European integration was mainly an affair of bargaining among national
elites. However, as the European Union (EU) grew wider and deeper, it became a highly
contested political issue with different national publics holding increasingly dissimilar
views about the EU and its future (De Vries, 2018; Hooghe and Marks, 2009).
Against this backdrop, a system of differentiated integration (DI) emerged, allowing to
accommodate this heterogeneity in preferences by granting the member states a possibil-
ity to vary levels of engagement in EU policy (Schimmelfennig and Winzen, 2020). Over
the years, and in light of the multiple crises that the EU has been facing, DI has become
commonplace in the EU’s legal order. In response to this development, a rapidly growing
body of literature has been devoted to understanding the causes, spatial patterns, and his-
torical trajectories of differentiation (Leruth et al., 2019; Schimmelfennig and Winzen,
2020). Despite these important advancements in the study of DI, research on public
opinion and differentiation is still lacking behind. Although studies are beginning to
address public opinion about DI (De Blok and De Vries, 2023; Hix et al., 2022), empirical
research on the reverse relationship, namely the consequences of differentiation for citi-
zens’EU attitudes, remains scarce (see Burk and Leuffen, 2019; but also see Schraff and
Schimmelfennig, 2020).
This is an important knowledge gap, given that the EU’s future critically hinges on
public support, making it crucial to understand the link between increasing differentiation
on the one hand, and EU public opinion on the other. Existing studies on DI tend to make
strong assumptions about the supposed effects of differentiation on citizens’EU attitudes
without testing them empirically. Conceiving the EU as an essentially “demoi-cratic”
polity, comprising multiple and diverse demoi (instead of a unified demos) (Bellamy
and Kröger, 2017; Cheneval and Schimmelfennig, 2013; Nicolaïdis, 2013), one stream
in the DI literature views differentiation as an adequate acknowledgement of the EU’s
diversity, leaving it up to each national political community to determine how much inte-
gration is enough integration (Lord, 2015: 792). From this perspective, DI is a valuable
tool to counter contemporary political challenges to integration, such as Euroscepticism,
by accommodating national preferences in sensitive policy areas, while facilitating
further integration among the willing.
In contrast, another stream in this literature has been much more critical of DI
(Adler-Nissen, 2014: 27–32; Schimmelfennig and Winzen, 2020: 176–186). Among
other things
1
, some argue that differentiation may be used to exclude member states
from certain policy areas to avoid costs (e.g., by restricting the free movement of
workers within the EU), thereby fostering discrimination and creating different classes
of EU citizens (see Schimmelfennig and Winzen, 2020: 180). Moreover, extending
these criticisms, DI may also be argued to potentially alienate Europhiles who desire
further integration but belong, at the same time, to a national political community that
opts out from a policy or is unwillingly excluded from it.
Based on these two streams of thought, DI can be seen as either part of the problem or
part of the solution to the various crises currently facing the EU and thus, it may or may
not be a desirable scenario for the EU’s future (European Commission, 2017). Yet, with
Vergioglou and Hegewald 207
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