A central bank's resource constraint bounds the dividends it can distribute by the present value of seignorage, which is a modest share of GDP. This is in spite of the mystique behind a central bank's balance sheet. Moreover, the statutes of the Federal Reserve or the ECB make it difficult for it to redistribute resources across regions. In a simple model of sovereign default, where multiple equilibria arise if debt repudiation lowers fiscal surpluses, the central bank may help to select one equilibrium. The central bank's main lever over fundamentals is to raise inflation, but otherwise the balance sheet gives it little leeway.

We propose a simple model of the sovereign-bank diabolic loop, and establish four results. First, the diabolic loop can be avoided by restricting banks' domestic sovereign exposures relative to their equity. Second, equity requirements can be lowered if banks only hold senior domestic sovereign debt. Third, such requirements shrink even further if banks only hold the senior tranche of an internationally diversified sovereign portfolio--known as ESBies in the euro-area context. Finally, ESBies generate more safe assets than domestic debt tranching alone; and, insofar as the diabolic loop is defused, the junior tranche generated by the securitization is itself risk-free.