Published online by Cambridge University Press: 03 July 2012
In international politics ‘friends’ co-ally. But friendship is relational and contextual. Countries are more likely to act on particular common interests if few other actors share that identity. In contrast, new cleavages are likely to emerge as an identity becomes ubiquitous. The tendency for states to form alliances based on certain affinities is thus best thought of as a variable, rather than as a constant. For example, in systems where democracies are scarce, democracies eagerly co-ally. As democracy becomes common, however, incentives binding democratic allies together weaken compared to other definitions of mutual interest. This argument, and the evidence we provide, suggest that the salience of identities as cues to affinity and difference vary with the distribution of types in the system.
Department of Political Science, University of California San Diego (email: egartzke@ucsd.edu); and Department of Political Science, University of Pennsylvania (email: weisiger@sas.upenn.edu), respectively. The authors thank Brett Benson, Kristian Gleditsch and anonymous reviewers for helpful comments and suggestions, and Mark Crescenzi and Andrew Enterline for use of their data on dyadic threats. An appendix containing additional information is available online at: http://dx.doi.org/10.1017/S0007123412000208.
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