The study of secession generally stresses the causal influence of cultural identities, political preferences or ecological factors. Whereas these different views are often considered to be mutually exclusive, this paper proposes a two-stage model in which they are complementary. We posit that cultural identities matter for explaining secessionism, but not because of primordial attachments.Rather, religious and linguistic groups matter because their members are imbued with cultural legacies that lead to distinct political preferences over welfare statism. Further, ecological constraints such as geography and topography affect social interaction with like-minded individuals. On the basis of both these political preferences and ecological constraints, individuals then make rational choices about the desirability of secession. Instrumental considerations are therefore crucial in explaining the decision to secede, but not in a conventional pocketbook manner. To examine this theory, we analyze the 2013 referendum on the secession of the Jura Bernois region from the canton of Berne in Switzerland, using municipal level census and referendum data. The results lend support to the theory and suggest one way in which the politics of identity, based on factors like language and religion, can be fused with the politics of interest (preferences for more or less state intervention into the polity and economy) to better understand group behavior.Keywords: Secession, referendum, welfare statism, cultural identities, ecological constraints, rational choice 2 Secession is a phenomenon that affects both the developing countries (e.g., Georgia, China, Russia, Ukraine, Nigeria) as well as developed ones (e.g., Spain, Canada, United Kingdom, France, Italy; Dion, 1996;Sorens, 2012). In several European democracies, like the United Kingdom and Spain (Muñoz and Guinjoan, 2013;Muñoz and Tormos, 2014), secessionist demands are accompanied by calls for a referendum to decide the question once and for all. In others, such as France, Belgium, and Italy, secession is at least sporadically invoked in political discourse when demanding more territorial group rights or fewer payments to poorer areas (Lindsey, 2012;Coppieters and Huysseune, 2002).Despite these developments in European politics, scholars continue to disagree over the relative importance of different mechanisms for understanding secession. Some argue that cultural factors, such as emotions, affect, and social identity, are key to explaining nationalism and separatism (e.g. Smith, 1986;Connor, 1994;Petersen, 2002), whereas others think that they can best be understood in terms of rational action (e.g. Buchanan and Faith, 1987;Wittman, 1991;Bolton and Roland, 1997;Bookman, 1992;Collier and Hoeffler, 2002;Sorens, 2012). Still others emphasize structural constraints on individual decision-making through geographically constrained social networks (Lipset and Rokkan, 1967;Jenkins, 1986;Rutherford et al., 2014). Thus whereas some scholars see secession as largely a matter of the he...