This paper presents the DIGNAR (Debt, Investment, Growth, and Natural Resources) model, which can be used to analyze the debt sustainability and macroeconomic effects of public investment plans in resource-abundant developing countries. DIGNAR is a dynamic, stochastic model of a small open economy. It has two types of households, including poor households with no access to financial markets, and features traded and nontraded sectors as well as a natural resource sector. Public capital enters production technologies, while public investment is subject to inefficiencies and absorptive capacity constraints. The government has access to different types of debt (concessional, domestic and external commercial) and a resource fund, which can be used to finance public investment plans. The resource fund can also serve as a buffer to absorb fiscal balances for given projections of resource revenues and public investment plans. When the fund is drawn down to its minimal value, a combination of external and domestic borrowing can be used to cover the fiscal gap in the short to medium run. Fiscal adjustments through tax rates and government non-capital expenditures—which may be constrained by ceilings and floors, respectively—are then triggered to maintain debt sustainability. The paper illustrates how the model can be particularly useful to assess debt sustainability in countries that borrow against future resource revenues to scale up public investment.

The last time global sovereign debt reached the level seen today was at the end of the Second World War, and this shaped a generation of economic policymaking. International institutions were transformed, country policies were often draconian and distortive, and many crises ensued. By the early 1970s, when debt fell back to pre-war levels, the world was radically different. It is likely that changes of a similar magnitude -for better and for worse - will play out over coming decades. Sovereign Debt: A Guide for Economists and Practitioners is an attempt to build some structure around the issues of sovereign debt to help guide economists, practitioners and policymakers through this complicated, but not intractable, subject. Sovereign Debt brings together some of the world's leading researchers and specialists in sovereign debt to cover a range of sub-disciplines within this vast topic. It explores debt management with debt sustainability; debt reduction policies with crisis prevention policies; and the history with the conjuncture. It is a foundation text for all those interested in sovereign debt, with a particular focus real world examples and issues.

Topics discussed in this publication include: an introduction to theoretical and practical aspects of fiscal sustainability; theoretical prerequisites for fiscal sustainability analysis; debt indicators in the measurement of vulnerability; cyclical adjustment of budget surplus; pro-cyclical fiscal policy using Mexico's fiscal accounts as a case study; fiscal rules and the experience of Chile; currency crises and models for deal with financing costs.

The paper offers an approach to assessing the sustainability of public debt taking into account the effect of fiscal policy on output, as well as uncertainty in the model parameters and system dynamics. Uncertainty is specified in general terms, and the analysis is based on the notion of invariant sets. Examples are provided to illustrate how the method can be applied in practice.