Why do governments default, and why don't they default more often?

This paper considers the economic and political drivers of sovereign default, focusing on countries rich enough to render sovereign default a ?won?t pay? rather than a ?can?t pay? phenomenon. Unlike many private contracts, sovereign debt contracts rely almost exclusively on self-enforcement rather than on third-party enforcement. Among the social costs of sovereign default are contagion and concentration risk, both within and outside the jurisdiction of the sovereign, and ?rule of law externalities?. We consider illiquidity as a separate trigger for sovereign default and emphasize the role of lenders of last resort for the sovereign. Not only do political economy factors drive sovereign insolvency, they also influence the debt sustainability analyses performed by national and international agencies. We consider it likely that the absence of sovereign defaults in the advanced economies since the (West) German defaults of 1948 and 1953 until the Greek defaults of 2012 was a historical aberration that is unlikely to be a reliable guide to the future.