We provide a theoretical study of the interplay between cross-country assistance and expectations-driven sovereign debt crises. A self-interested "safe" country may choose to assist a "risky" country that is prone to default. Investors internalize the potential for assistance when lending to fragile countries. If the safe country is not able to commit to or rule out cross-country transfers, assistance only improves the equilibrium outcomes if the risky country is fundamentally insolvent and cannot handle its debt even at the risk-free interest rate. If a default requires pessimistic expectations, an incentive-compatible assistance policy has adverse side effects.
In this paper, I derive and apply three univariate methods and one bi-variate method to estimate permanent and transitory components of the American output growth path during the 1790 to 2017 period. The results show that statistical tests give little support to the hypothesis of significant permanent growth rate changes (univariate methods). The "special century" (1870-1970, as defined by Gordon (2016)) exhibited more volatile permanent shifts in the output level compared to recent decades (bivariate method).
