Public debt, bailouts, and common bonds

We look at a model where countries of different sizes provide local public goods with positive spillovers. Matching grants can give rise to optimal expenditure levels, but countries can induce bailouts. We study the characteristics of these bailouts in a subgame-perfect Nash equilibrium and how these characteristics are affected by the introduction of common bonds. Partial substitution of common for sovereign bonds has two implications. First, it lowers the average and marginal borrowing costs of countries which may be eligible for bailouts. This effect leads to higher borrowing in these countries irrespective of their bailout expectations. Second, the lower borrowing costs mitigate the incentives of countries to induce a bailout and, therefore, constrain the parameter set for which a soft budget constraint equilibrium exists. As a result, the introduction of common bonds can also be in the interest of those countries that provide the bailouts.