Non-technical summary
Sovereign debt defaults by Russia (in 1998) and Argentina (in 2001) as well as theoutbreak of the European sovereign debt crisis, which reached an initial peak withthe Greek default in 2012, have shown that sovereign debt defaults are by no meansrare events, despite the significant costs they entail. This has revived and stimulatedrenewed interest in this topic among academics and policymakers alike.A key question arising in such circumstances is whether default was optimal forthe sovereign given the costs associated with default? This paper addresses the ques-tion of optimal sovereign default in a model in which a domestic government issuesnon-contingent bonds to foreign investors and makes optimal repayment decisions onthese bonds. We show that it can be optimal to occasionally deviate from the legalrepayment obligation, even if such deviations give rise to significant default costs.Such deviations improve ex-ante welfare and contribute to insuring output risk andenhancing the efficiency of investment decisions. Default can be optimal followingadverse shocks to domestic productivity, especially if the country has a high debt-to-GDP ratio. Our quantitative analysis reveals, however, that for empirically plausibledebt-to-GDP ratios and default costs, the decision to default is optimal only in re-sponse to disaster-like shocks to domestic output.