Corporate-Sovereign Debt Nexus and Externalities

I build a dynamic quantitative model in which both firms and the government can default. Rising endogenous corporate debt increases sovereign default risk, as tax revenues are expected to decrease. Externalities arise because it can be privately optimal but socially suboptimal for firms to default given their limited liability, rationalizing macroprudential interventions in corporate debt markets. I propose a set of such optimal policies that reduce the number of defaulting firms, increase fiscal space, and boost household consumption during financial crises. Contrary to conventional wisdom, countercyclical debt policy can be counterproductive, as the countercyclical policy induces more firmdefaults.