Expectation vs. Reality: political effects of DI on EU support and institutional trust

Previous research on differentiated integration (DI) paid considerable attention to its causes. Nevertheless, we know very little about the political, societal and economic consequences of DI. This paper delves into the largely unexplored territory of DI effects on trust and support for the European Union and its institutions. Using variations of the synthetic control method, we investigate the reactions of European publics to events of primary law differentiation between 1980 and 2019. Our preliminary results indicate member-states (MS) receiving a requested opt-out as well as MS allowed to integrate into a policy area that previously excluded them, increase their trust in EU institutions. At the same time, not receiving a highly demanded opt-out and being excluded from integration is detrimental to trust. With sufficient data, the empirical framework of this study is a suitable paradigm for further research on effects of DI.