Referendums on sovereignty have proliferated in recent years and are increasingly catching the interest of political scientists. A growing literature examines the conditions leading to referendums on sovereignty matters, whether sovereignty referendums help to resolve conflicts peacefully, and various other outcomes of sovereignty referendums. An indispensable prerequisite for many of these research questions is a well-researched, complete compilation of the worldwide experience with sovereignty referendums. This is where the Contested Sovereignty dataset steps in.
Departing from an improved conceptualization of what does and does not constitute a `sovereignty referendum’, the Contested Sovereignty dataset records the worldwide incidence of sovereignty referendums from 1776-2012. Drawing on a rich set of sources, the dataset identifies a total of 602 sovereignty referendums, more than double the number in existing lists. Further, the dataset categorizes sovereignty referendums into several different types (e.g., unification, autonomy, and independence referendums).
The data and documentation can be downloaded here.
When referring to this data set, please always cite:
Aubert, Nicolas, Micha Germann, and Fernando Mendez (2015). ``Contested Sovereignty: A Global Compilation of Sovereignty Referendums (1776_2012). Codebook v.1.0.’’ University of Zurich, unpublished manuscript. 
Work on this dataset was funded by the Swiss National Science Foundation (grant no. 135127).
An update of this dataset is currently in progress. Provisional data extending coverage to 2017 can be obtained upon request.