In our incomplete markets economy households choose portfolios consisting of risky (uninsurable) capital and money. Money is a bubble, it has positive value even though it yields no payoff. The market outcome is constrained Pareto inefficient due to a pecuniary externality. Each individual agent takes the real interest rate as given, while in the aggregate it is driven by the economic growth rate, which in turn depends on individual portfolio decisions. Higher inflation due to higher money growth lowers the real interest rate on money and tilts the portfolio choice towards physical capital investment. Modest inflation boosts growth rate and welfare.

We propose a measure of systemic risk, Δ CoVaR, defined as the change in the value at risk of the financial system conditional on an institution being under distress relative to its median state. Our estimates show that characteristics such as leverage, size, maturity mismatch, and asset price booms significantly predict Δ CoVaR. We also provide out-of-sample forecasts of a countercyclical, forward-looking measure of systemic risk, and show that the 2006:IV value of this measure would have predicted more than one-third of realized Δ CoVaR during the 2007–2009 financial crisis. (JEL C58, E32, G01, G12, G17, G20, G32)

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.