A quarterly magazine of the IMF

December 2002, Volume 39, Number 4

As part of the work on vulnerability indicators, economists are looking at what level of debt is sustainable for an economy and how much is too much. Borrowing from abroad can help countries grow faster by financing productive investment, and it can also cushion the impact of economic disruptions. But if a country or government accumulates debt beyond what it is able to service, a debt crisis can erupt with potentially large economic and social costs. For this reason, it is important to gauge how much debt an economy or government can safely handle. This assessment is particularly relevant in emerging market economies that rely heavily on global capital markets to meet their large financing needs.

What exactly is debt sustainability? It may be defined as a situation in which a borrower is expected to continue servicing its debts without an unrealistically large future correction to its balance of income and expenditure. Conversely, debt becomes unsustainable when it accumulates at a faster rate than the borrower's capacity to service it. Working out what level of debt is sustainable requires an assessment of how outstanding stocks of liabilities are likely to evolve over time, as well as assumptions about future interest rates, exchange rates, and trends in income. Like any assessment requiring assumptions about the future, this is difficult to get right.

• forming a view of how outstanding stocks of liabilities are likely to evolve over time relative to the economy's (or the government's) ability to pay;
• examining how the outlook would change under plausible shocks; and
• assessing whether the results may lead to an unsustainable situation, as defined above.

The first step involves projecting the flows of revenues and expenditures—including those for servicing debt—as well as key macroeconomic variables, such as interest rates, rates of economic growth, and exchange rate changes (given the currency denomination of the debt). To the extent that these variables are influenced by government policies, projections of debt dynamics depend on policy variables as well as on macroeconomic and financial market developments that are intrinsically uncertain.

Given the uncertainties, it is important to explore, in a second step, what the risks are. Among the main ones are higher costs of financing, which may reflect general developments in financial markets—including possible spillover effects from other countries in difficulty—or funding problems specific to the country in question. Similarly, a sharp exchange rate depreciation, possibly—though not necessarily—in the aftermath of the collapse of an exchange rate peg, can drastically increase the burden of foreign-currency-denominated debt. Indeed, as some recent cases have shown, once a crisis erupts, the magnitude of capital outflows can result in exchange rate adjustments far in excess of any initial estimates of overvaluation, as happened, for example, in Indonesia during its 1997-98 crisis.

Another important source of uncertainty surrounding projections of debt and debt service is contingent claims—such as those associated with either explicit or implicit guarantees of debt or bank deposits. Many contingent claims, by their nature, pass unnoticed in normal times but are more likely to be exercised in crises. Such claims have been a key feature in recent emerging market crises, in which defaults in one sector have spilled over to others. But contingent claims are exceedingly difficult to measure in practice, both because amounts subject to such claims are often unknown and because the terms of the claims—the precise circumstances in which they would turn into actual liabilities—are often unknowable.

The third step—and arguably the most difficult in a debt sustainability assessment—is defining a threshold at which debt is deemed to become unsustainable. Such thresholds have been established in certain instances for particular groups of countries. For heavily indebted poor countries, for example, levels above 200 percent for the net present value of debt as a share of export earnings were empirically associated with a significantly higher incidence of debt restructurings. For other nonindustrial countries, there is some evidence that a 40 percent debt-to-GDP ratio is a turning point at which risks of debt exposures start to increase. However, this result reflects the typical conditions in the countries studied, including a relatively low level of foreign assets. More generally, a serious note of caution is required when applying a debt threshold to individual countries. No single threshold can reliably define the turning point at which a country's debt will prove unsustainable, as country-specific factors and circumstances beyond the debt ratio play important roles. For example, higher debt ratios are less worrisome for countries with faster export growth, a larger share of exports to GDP, and a larger share of domestic-currency debt.

Ultimately, assessments of sustainability are probabilistic: one can normally envisage some states of the world in which a country's debt would be sustainable and others in which it would not. There is always an element of judgment involved in assessing whether an individual country's debt exceeds prudent levels.

• medium-term projections of the balance of payments and of fiscal developments—a staple of the IMF's work on member countries, particularly as part of an IMF lending program;
• assessments of medium-term current account and real exchange rate sustainability, which have a bearing on public and external debt sustainability, especially when there is significant foreign-currency-denominated debt; and
• financial sector stability assessments, a more recent addition to the IMF's toolkit; they help identify the vulnerability of the financial sector to various shocks, with potentially important implications for the contingent liabilities of the government.

Building on these elements, the IMF has recently developed a standardized framework for assessing debt sustainability. The framework explores both fiscal and external debt sustainability and centers on the IMF's baseline medium-term projections for a country's economy. Beyond the baseline projections for public and external debt, the framework incorporates a standard set of sensitivity tests that generate the debt dynamics under alternative assumptions about key variables (including economic growth, interest rates, and the exchange rate). These alternative assumptions are calibrated on the basis of each country's own history, as reflected in averages and volatility of the respective variables in the past.

The new framework may be useful in three different situations. For countries that have moderately high indebtedness but are not facing an imminent crisis, the framework can help identify vulnerabilities—that is, how the country might eventually stray into "insolvency territory." For countries that are on the brink, or in the midst, of a crisis, experiencing severe stress characterized by high borrowing costs or lack of market access, the framework can be used to examine the plausibility of the debt-stabilizing dynamics articulated in the program projections. Finally, in the aftermath of a default, the framework can be used to explore the debt dynamics following a potential restructuring.

Application of the framework is still new but will be progressively expanded to a wide range of countries, both for surveillance purposes and to inform decisions about IMF financial support of programs, with appropriate modifications in light of initial experience. Although the purpose is to provide greater uniformity and discipline for sustainability assessments, it is not intended that the framework be applied in a completely mechanical and rigid fashion: depending on country circumstances, there may be good reasons for deviating from it to some extent. At the same time, the basic logic of undertaking baseline sustainability analyses and calibrated sensitivity tests should apply across countries. Finally, in interpreting the results generated by the framework, additional factors need to be considered, such as the structure of the debt (in terms of its maturity composition, whether it is contracted on fixed or floating rates, whether it is indexed, and by whom it is held) as well as various other vulnerability indicators. Information provided by markets, including expectations of interest rates and spreads embedded in the position and shape of yield curves, access to new borrowing, and whether there have been interruptions in such access or difficulties in issuing long-term debt, will also put the figures in perspective.

This article is based on "Assessing Sustainability," a paper prepared by the IMF's Policy Development and Review Department, May 28, 2002.