National Debt Sustainability and the Dynamics in the Economy of Diamond.

We analyze the effect of a constant debt policy on capital accumulation and provide an in--depth treatment of the dynamics in the economy of Diamond. We derive the conditions for avoiding a debt crisis in both the short-run and the long-run and provide geometrical tools to analyze the issue of sustainability. There is always a level of debt ensuring that any level of capital between 0 and an upper limit, and in particular the Golden rule equilibrium, exists as a steady-state equilibrium, yet it is not necessarily stable. We also discuss poverty trap issues.