National or Supranational? Why and How Citizens Vote in Sovereignty Referendums in the European Union

Referendums have become an important tool of sovereignty reallocation addressing domestic and supranational issues in the EU. Comparative studies within and across different levels of decision-making are nonetheless rare. The growing use of direct democratic instruments represents a new and understudied phenomenon in European elections which allows for systematic analyses within and across geographical and topical subgroups. Do similar mechanisms drive turnout and voting decisions across different referendum types? Capitalising on the high degree of comparability of ballot issues and background conditions across EU members, we analyse survey data from referendums on EU matters and (sub-)national sovereignty referendums addressing regional self-determination demands between 1990 and 2017. We argue that turnout and vote choice are determined by comparable mechanisms on both levels, and show that education and income, as well as information costs inform voters’ decisions. While the actual state of the economy is not a strong predictor, voters' assessments of both personal and national economic conditions are significant for vote choice. The findings highlight the shared traits of decision-making processes across different referendum types in advanced democracies and offer new avenues for research that seeks to account for vote choices in direct-democratic processes.