To fight or to vote: Sovereignty referendums as strategies in conflicts over self-determination

Subnational groups employ a variety of strategies to contest governments. While democratic states offer a broader array of accessible options, autocratic regimes are more difficult to contest via conventional means. Why do subnational groups stage sovereignty referendums across regime types? Our argument is that public votes over greater autonomy or independence signal adherence to international democratic norms and the legitimacy of the demand towards three audiences: the state, the domestic population, and the international community. Self-determination groups seek to gain support from their domestic constituency as well as the international community in order to pressure the state government into granting concessions. We introduce a new dataset of referendums and international diplomacy by subnational self-determination groups on a global scale between 1990 and 2015. We supplement the descriptive evidence and assess the plausibility of the proposed mechanism with an out-of-sample case of an in-sample observation, the 2017 independence referendum in Iraqi Kurdistan. We show that referendums are indeed associated with international diplomacy and domestic state building by self-determination groups, suggesting that both tools are critical for the choice of conventional strategies across regime types.