Differentiated integration in the European Union: Institutional effects, public opinion, and alternative flexibility arrangements
| Author | Frank Schimmelfennig,Dirk Leuffen,Catherine E De Vries |
| DOI | http://doi.org/10.1177/14651165221119083 |
| Published date | 01 March 2023 |
| Date | 01 March 2023 |
| Subject Matter | Articles |
Differentiated integration
in the European Union:
Institutional effects, public
opinion, and alternative
flexibility arrangements
Frank Schimmelfennig
Center for Comparative and International Studies, ETH Zurich,
Zurich, Switzerland
Dirk Leuffen
Department of Politics and Public Administration, University of
Konstanz, Konstanz, Germany
Catherine E De Vries
Department of Social and Political Sciences, Bocconi University,
Milan, Italy
Abstract
Research on differentiated integration (DI) in the European Union (EU) has focused on
the causes, conditions, and patterns of differentiation in European integration. By con-
trast, we know less about its effects on institutional outcomes and public support; more-
over, alternatives to de jure DI in providing flexibility are still rarely accounted for. This
introduction to the special issue takes stock of, and discusses omissions, in the current
literature on DI. We propose an analytical framework, centering on efficiency and legit-
imacy, to study the effects of different types of DI. We use this framework to motivate
the choice and assess the contributions of the articles selected for this special issue.
Keywords
Differentiated integration, efficiency, European Union, legitimacy
Corresponding author:
Frank Schimmelfennig, Center for Comparative and International Studies, ETH Zurich, Haldeneggsteig 4,
8092 Zurich, Switzerland.
Email: frank.schimmelfennig@eup.gess.ethz.ch
Article
European Union Politics
2023, Vol. 24(1) 3–20
© The Author(s) 2022
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DOI: 10.1177/14651165221119083
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Introduction
Research is quickly catching up with the reality of differentiated integration (DI) in the
European Union (EU). Transitional arrangements granting member states temporary
derogations from the application of European legislation have been in use since the
very beginnings of integration into the European Economic Community. Such transitory
differentiation has enjoyed particularly frequent use in the context of the accession of new
member states. Since the 1990s, the EU has further experienced a series of open-ended
differentiations for extant member states. The best-known examples are the Eurozone
and the Schengen Area: both have exempted members unwilling to participate, and
both continue to exclude members that do not meet the prerequisites. In parallel to this
internal differentiation, the EU has created a variety of external differentiation
schemes, which allow non-members to participate selectively in EU policies, starting
with trade and association agreements in the 1960s and 1970s and culminating in the
European Economic Area (EEA) that entered into force in 1994.
Academic work has accompanied the growth of DI, but it initially remained predom-
inantly conceptual and prescriptive, suggesting and categorizing alternative ways in
which the EU could develop away from the model of uniform integration (see
Holzinger and Schimmelfennig, 2012 for an overview). By contrast, the major general
theories of European integration did not pay systematic attention to differentiation, and
theory-guided empirical work was extremely rare—Kölliker’s (2001, 2006) application
of collective goods theory to DI being the main exception.
In the past decade, the situation has changed massively. Recent research has included
differentiation in the theory, definition, and measurement of integration and has engaged
in systematic data collection and analysis (Duttle, 2016; Duttle et al., 2017; Leuffen et al.,
2013; Schimmelfennig and Winzen, 2014, 2019, 2020). Related works have explored
other forms of flexibility in EU legislation and implementation beyond the legal exemp-
tion or exclusion of member states (Franchino, 2006; Steunenberg and Toshkov, 2009;
Zhelyazkova and Thomann, 2022).
DI research has received a further boost from contemporary developments in
European integration as well as from EU funding support. Whereas the reform debate
on the Future of Europe included internal differentiation as one option (Commission,
2017), the Brexit negotiations have put external differentiation in the spotlight.
Moreover, the EU’s Horizon 2020 program for research and innovation has funded
four collaborative projects on DI to advance the research agenda and consolidate research
networks.
1
In short, DI has shifted from a marginal to a mainstream topic in EU research
(Leruth et al., 2019, 2022).
At the same time, systematic blind spots remain. Research has focused on the causes,
conditions, and patterns of differentiation in European integration. It has sought to
explain why member states choose differentiation, under which conditions DI is more
or less likely to occur and endure, and how it develops over time and across countries
(Schimmelfennig and Winzen, 2020; Schimmelfennig et al., 2015).
By contrast, we know less about its institutional and public opinion effects. Does DI
facilitate EU decision making, strengthen democratic procedures, and improve the
4European Union Politics 24(1)
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