Indian Economy·Explained

Debt Sustainability — Explained

Updated 7 Mar 2026

Detailed Explanation

Debt sustainability is a cornerstone of sound macroeconomic management, ensuring that a nation's fiscal policies do not lead to an unmanageable accumulation of public debt. For UPSC aspirants, a deep dive into this concept requires understanding its theoretical underpinnings, India's specific context, and the policy tools employed to maintain fiscal health.

I. Origin and Historical Evolution of India's Debt Dynamics

India's journey with public debt has been marked by distinct phases, each shaping its approach to fiscal management:

1990s Fiscal Crisis (Early 1990s): — India faced a severe balance of payments crisis, exacerbated by high fiscal deficits and rising public debt. The debt-to-GDP ratio for the Centre was around 60% in 1991, with interest payments consuming a significant portion of revenue. This crisis underscored the urgent need for fiscal reforms.

Post-1991 Reforms Era: — The economic liberalization reforms initiated in 1991 aimed at fiscal consolidation, reducing subsidies, and improving tax administration. This period saw efforts to rein in deficits, though progress was often uneven.

FRBM Era (2003 onwards): — The Fiscal Responsibility and Budget Management (FRBM) Act, 2003, was a landmark legislative step to institutionalize fiscal discipline. It mandated targets for reducing revenue and fiscal deficits and aimed to eliminate revenue deficit by 2007-08. While the initial targets were missed due to global financial crises and other factors, the Act provided a statutory framework for fiscal prudence. The N.K. Singh Committee (FRBM Review Committee) in 2017 recommended a debt-to-GDP ratio of 60% for the general government (Centre + States) by 2023, comprising 40% for the Centre and 20% for states.

Post-2008 Global Financial Crisis: — The crisis necessitated counter-cyclical fiscal expansion, leading to a temporary relaxation of FRBM targets. India's debt-to-GDP ratio saw an uptick, but the economy's resilience helped manage the situation.

COVID-19 Era Debt Dynamics (2020-2023): — The pandemic triggered an unprecedented fiscal response globally, including in India. To mitigate the economic fallout, both central and state governments significantly increased spending and borrowing. India's general government debt-to-GDP ratio, which was around 74% in FY2019-20, surged to over 90% in FY2020-21. Interest payments as a percentage of revenue receipts also increased, highlighting the growing interest burden. This period underscored the trade-off between immediate crisis response and long-term debt sustainability, necessitating a credible fiscal consolidation path post-pandemic.

II. Constitutional and Statutory Basis for Borrowing

Constitutional Provisions:

* Article 292 (Union Borrowing): Empowers the Union government to borrow on the security of the Consolidated Fund of India, within limits set by Parliament. This provides the legal basis for central government debt.

Parliament has enacted laws to regulate this, though a comprehensive law setting specific limits has not been consistently in force, relying more on annual budget approvals and the FRBM Act. * Article 293 (State Borrowing): Grants states the power to borrow within India on the security of their Consolidated Funds, subject to limits set by their respective legislatures.

A crucial provision, Article 293(3), states that a state cannot raise any loan without the consent of the Government of India if it owes any outstanding loan to the Centre or has a guarantee outstanding given by the Centre.

This gives the Centre significant control over state borrowing, especially for financially weaker states. This is a key mechanism for the Centre to influence state debt sustainability.

FRBM Act, 2003 (and Amendments): — The FRBM Act is the primary statutory framework for fiscal discipline. It aims to ensure inter-generational equity in fiscal management and long-term macroeconomic stability. Key provisions include:

Targets for fiscal deficit, revenue deficit, and public debt. (For specific details, refer to ). Mandatory presentation of Medium Term Fiscal Policy Statement, Fiscal Policy Strategy Statement, and Macroeconomic Framework Statement in Parliament, enhancing transparency and accountability. * Escape clauses allowing deviation from targets under specific circumstances (e.g., national security, calamity, structural reforms).

Role of Parliament/State Legislatures: — These bodies authorize borrowing through annual appropriation acts and, potentially, specific debt limit laws. This legislative oversight is crucial for democratic accountability in debt management.

III. Debt Sustainability Analysis (DSA) Methodologies

DSA is a framework used to assess a country's ability to service its debt over the medium to long term. It typically involves:

IMF-World Bank DSA Framework: — This is a widely used framework, especially for low-income and emerging market economies. It involves:

* Baseline Scenario: Projecting debt indicators (e.g., debt-to-GDP ratio) under realistic macroeconomic assumptions (growth, interest rates, primary balance, exchange rates). * Stress Tests/Sensitivity Analysis: Assessing how debt indicators would evolve under various adverse shocks (e.

g., lower growth, higher interest rates, primary balance deterioration, exchange rate depreciation, natural disasters). This helps identify vulnerabilities. * Stochastic Debt Projections: Using probabilistic methods to generate a range of possible debt trajectories, rather than just a single baseline, reflecting the uncertainty of future economic variables.

Debt-to-GDP Ratio Dynamics Equation: — The evolution of the public debt-to-GDP ratio (d) over time is governed by the following equation:

d_t = [(1+r)/(1+g)] * d_{t-1} - pb_t / (1+g) Where: `d_t` = Debt-to-GDP ratio in the current period (t) d_{t-1} = Debt-to-GDP ratio in the previous period (t-1) `r` = Nominal interest rate on government debt g = Nominal GDP growth rate * pb_t = Primary balance-to-GDP ratio in period t (positive for surplus, negative for deficit)

Explanation: This equation shows that the debt ratio increases if the 'snowball effect' (where interest payments exceed GDP growth, i.e., r > g) is strong, and if there is a primary deficit (negative pb). Conversely, a primary surplus and strong GDP growth relative to interest rates help reduce the debt ratio.

Worked Numerical Example (Calibrated to India):

* Baseline Scenario (Pre-COVID, FY2019-20): `d_{t-1}` (FY19-20 General Government Debt-to-GDP) ≈ 74% r (Average nominal interest rate) ≈ 6.5% `g` (Nominal GDP growth rate) ≈ 7.5% pb_t (Primary Balance-to-GDP) ≈ -3.5% (deficit)

d_t = [(1+0.065)/(1+0.075)] * 0.74 - (-0.035) / (1+0.075) d_t = [1.065/1.075] * 0.74 + 0.035 / 1.075 d_t = 0.99069 * 0.74 + 0.03256 d_t = 0.7320 + 0.03256 = 0.765 or 76.5% (This shows a slight increase even pre-COVID, indicating underlying pressures).

* Shock Scenario (COVID-19 Impact, FY2020-21): `d_{t-1}` (FY19-20 General Government Debt-to-GDP) ≈ 74% r (Average nominal interest rate) ≈ 6.5% (assumed stable for simplicity) `g` (Nominal GDP growth rate) ≈ -3.0% (significant contraction) pb_t (Primary Balance-to-GDP) ≈ -7.0% (due to increased spending, revenue loss)

d_t = [(1+0.065)/(1-0.030)] * 0.74 - (-0.070) / (1-0.030) d_t = [1.065/0.970] * 0.74 + 0.070 / 0.970 d_t = 1.0979 * 0.74 + 0.07216 d_t = 0.8124 + 0.07216 = 0.88456 or 88.5% (This illustrates the sharp increase in debt-to-GDP during the pandemic, aligning with actual trends where it crossed 90%).

Debt-Stabilizing Growth Rate: — This is the nominal GDP growth rate required to keep the debt-to-GDP ratio constant, given the interest rate and primary balance. It can be derived by setting d_t = d_{t-1} in the dynamics equation and solving for g. If actual growth is consistently below this rate, debt will tend to rise.

IV. Practical Functioning and Policy Observations

15th Finance Commission Observations: — The 15th FC (2020-25) expressed serious concerns about the rising debt levels of both the Centre and states, especially in the wake of the pandemic. It recommended a glide path for fiscal consolidation, aiming for the general government debt-to-GDP ratio to decline to 60% by FY2025-26. It also emphasized the need for a new FRBM-like framework for states, given their increasing fiscal autonomy and borrowing. The Commission highlighted the importance of off-budget borrowings and contingent liabilities in assessing true debt levels.

RBI State Debt Sustainability Reports: — The Reserve Bank of India regularly publishes reports and articles assessing the fiscal health and debt sustainability of Indian states. These reports often highlight states with high debt-to-GSDP ratios, large interest burdens, and significant contingent liabilities, flagging them for potential fiscal stress. The RBI advocates for prudent fiscal management, revenue augmentation, and expenditure rationalization by states.

Economic Survey Recommendations: — The annual Economic Survey consistently provides an assessment of India's fiscal situation and offers policy recommendations. It often emphasizes the need for fiscal consolidation, particularly through revenue buoyancy and rationalization of non-essential expenditure. Post-pandemic, the Surveys have focused on the importance of a credible medium-term fiscal framework, asset monetization, and structural reforms to boost growth and thereby improve debt sustainability.

V. India-Specific Thresholds and Benchmarks

While there's no universally agreed 'safe' debt-to-GDP ratio, several benchmarks are referenced:

FRBM Review Committee (N.K. Singh Committee): — Recommended a general government debt-to-GDP ratio of 60% by FY2023, split as 40% for the Centre and 20% for states. This is a key policy benchmark for India.

International Benchmarks: — For emerging economies, a debt-to-GDP ratio exceeding 70-80% is often considered a point of concern, though the specific threshold depends on factors like growth potential, institutional quality, and debt composition (domestic vs. external, currency of denomination). For developed economies, this threshold can be higher.

External Debt Vulnerability: — Indicators like external debt-to-GDP ratio, short-term external debt-to-reserves ratio, and debt service ratio (debt service payments as % of current account receipts) are used. India's external debt has historically been well-managed, with a relatively low share of short-term debt and comfortable foreign exchange reserves, making it less vulnerable to external shocks compared to many other emerging markets.

VI. Criticism and Challenges in DSA

Assumptions Sensitivity: — DSA results are highly sensitive to underlying assumptions about growth, interest rates, and primary balance. Small changes in these assumptions can significantly alter debt projections.

Ignoring Contingent Liabilities: — DSAs often focus on explicit government debt, potentially overlooking significant contingent liabilities (e.g., guarantees to PSUs, implicit liabilities from public sector banks) that can materialize and add to the debt burden.

Growth-Debt Nexus: — The relationship between debt and growth is complex. While high debt can hinder growth, low growth also makes debt unsustainable. Disentangling causality is challenging.

Political Economy Factors: — Fiscal consolidation often involves difficult political choices (e.g., cutting subsidies, raising taxes) that may not be feasible in the short term, leading to persistent deficits.

VII. Recent Developments and Current Affairs Hooks

Post-Pandemic Fiscal Challenges (2024-2026): — India continues to navigate the aftermath of the COVID-19 fiscal expansion. The central government has embarked on a fiscal consolidation path, aiming to reduce the fiscal deficit to 4.5% of GDP by FY2025-26. However, achieving this requires sustained revenue growth and expenditure rationalization. The challenge is to consolidate without stifling economic recovery.

State Government Debt Stress Cases (2024): — Several Indian states continue to face significant fiscal stress, with high debt-to-GSDP ratios (e.g., Punjab, Rajasthan, Kerala, West Bengal often cited in RBI reports). Their interest payments consume a large share of their revenue, limiting their ability to spend on development. The Centre has provided some support but also urged states to adhere to fiscal discipline. The issue of 'freebies' or populist spending by states has also drawn attention from the RBI and the Supreme Court, raising concerns about its impact on state debt sustainability.

International Initiatives (G20/Common Framework): — Globally, the G20 and Paris Club have introduced the 'Common Framework for Debt Treatments' beyond the Debt Service Suspension Initiative (DSSI) to address the debt vulnerabilities of low-income countries, especially post-pandemic. While India is a creditor in some cases, it also participates in global discussions on sovereign debt restructuring and transparency, reflecting its commitment to global financial stability.

VIII. Vyyuha Analysis: India's Debt Trajectory and Policy Implications

Vyyuha's analysis suggests that India's debt sustainability trajectory, while challenged by the COVID-19 pandemic, remains manageable due to several mitigating factors, primarily the dominance of domestic debt and a relatively robust growth outlook. However, complacency would be a grave error. The interplay of growth (g), interest rate (r), and primary balance (pb) is central to this assessment.

Interplay of g, r, and pb: — For India, the 'r-g' differential (interest rate minus growth rate) is a critical determinant. Historically, India has often enjoyed a positive 'g-r' differential (growth exceeding interest rates), which acts as a powerful force for debt reduction. Even if the government runs a modest primary deficit, strong nominal GDP growth can 'grow out' of debt. However, the pandemic temporarily reversed this, with growth plummeting and interest rates remaining sticky. Vyyuha emphasizes that maintaining a positive 'g-r' differential through sustained high nominal growth is paramount. This requires structural reforms to boost potential growth and prudent monetary policy (refer to for monetary policy transmission affecting debt costs) to keep interest rates stable and low without fueling inflation. Simultaneously, improving the primary balance through revenue buoyancy (e.g., GST reforms, direct tax compliance) and rationalizing unproductive expenditure is indispensable. The challenge lies in achieving this balance without resorting to pro-cyclical fiscal contraction that could derail growth.

Static vs. Dynamic Measures: — While India's current general government debt-to-GDP ratio (around 82% as of FY2023-24 estimates) appears high compared to the N.K. Singh Committee's 60% target, a dynamic assessment offers a more nuanced picture. The composition of India's debt, largely domestic and denominated in local currency, reduces external vulnerability. However, the rising interest burden on domestic debt, consuming a significant portion of revenue, highlights a dynamic vulnerability. Vyyuha stresses that static ratios, while useful for snapshots, must always be interpreted in the context of dynamic projections and the underlying economic fundamentals.

Policy Implications: Fiscal Consolidation vs. Growth Trade-offs: — The post-pandemic period presents a classic dilemma: aggressive fiscal consolidation could dampen nascent economic recovery, while delayed consolidation risks entrenching high debt levels and interest burdens. Vyyuha's view is that a balanced approach is needed. This involves a credible, gradual glide path for fiscal deficit reduction, coupled with growth-enhancing structural reforms (e.g., infrastructure investment, ease of doing business, skill development). Asset monetization, as advocated by the government, can also play a role in reducing debt without cutting essential capital expenditure. Furthermore, strengthening the fiscal capacity of states and ensuring their adherence to fiscal responsibility norms is crucial, given their significant share in general government debt. The focus should be on improving the quality of fiscal adjustment – prioritizing capital expenditure over revenue expenditure, and enhancing the efficiency of public spending. This approach ensures that fiscal policy supports long-term growth while gradually bringing debt ratios to a sustainable path. The implications for credit ratings (refer to ) are also significant, as sustainable debt management enhances investor confidence and reduces borrowing costs.

Often confused with

Side-by-side differences the UPSC paper likes to test.

Debt Sustainability vs Static vs. Dynamic Debt Sustainability Measures

Aspect	Debt Sustainability	Static vs. Dynamic Debt Sustainability Measures
Nature of Assessment	Static: Snapshot at a single point in time.	Dynamic: Projects debt trajectory into the future, considering evolution over time.
Key Indicators	Static: Current Debt-to-GDP ratio, Debt-to-Revenue ratio.	Dynamic: Debt dynamics equation, r-g differential, primary balance requirements, stress tests.
Policy Relevance	Static: Provides a current status report, useful for immediate comparison.	Dynamic: More relevant for policy formulation, identifying future risks and guiding fiscal strategy.
Complexity	Static: Relatively simpler to calculate and interpret.	Dynamic: More complex, involves projections, assumptions, and sensitivity analysis.
Forecasting Ability	Static: Limited forecasting ability, doesn't predict future trends.	Dynamic: Strong forecasting ability, helps anticipate potential debt crises under different scenarios.

From a UPSC perspective, understanding the distinction between static and dynamic debt sustainability measures is crucial. Static measures, like the debt-to-GDP ratio, offer a momentary snapshot of a nation's fiscal health.

While informative, they do not reveal whether current policies are sustainable in the long run. Dynamic measures, on the other hand, provide a forward-looking assessment, projecting how debt ratios will evolve under various economic and policy assumptions.

They incorporate factors like economic growth, interest rates, and fiscal balances to model future debt trajectories, often including stress tests for adverse scenarios. Vyyuha's analysis emphasizes that a comprehensive understanding of debt sustainability requires integrating both perspectives, as dynamic analysis informs policy adjustments needed to steer the debt path towards sustainability.

Why it is tested: High-probability conceptual question for both Prelims and Mains, testing fundamental understanding of debt analysis.

Debt Sustainability vs Central Government vs. State Government Debt Sustainability

Aspect	Debt Sustainability	Central Government vs. State Government Debt Sustainability
Borrowing Powers	Central: Article 292, Parliament sets limits. Can borrow domestically and externally.	State: Article 293, State Legislature sets limits. Primarily domestic borrowing. Requires Centre's consent if outstanding loan from Centre.
Fiscal Space	Central: Broader tax base (income tax, corporate tax, customs, GST share), monetary policy influence.	State: Limited tax base (GST share, state excise, stamp duty, property tax), no monetary policy tools.
Debt Composition	Central: Mix of market loans, small savings, external debt. Higher share of market borrowings.	State: Predominantly market loans (State Development Loans - SDLs), loans from Centre, provident funds. Very limited external debt.
Oversight/Regulation	Central: FRBM Act, parliamentary oversight, RBI as debt manager.	State: State FRBM Acts, state legislature oversight, Centre's consent for borrowing (Art 293(3)), RBI advises on SDLs.
Vulnerabilities	Central: Large overall debt stock, global economic shocks, interest rate volatility.	State: Limited revenue autonomy, populist spending ('freebies'), contingent liabilities (guarantees), dependence on central transfers.

Debt sustainability for the Central and State governments in India presents distinct challenges and frameworks. The Central government, under Article 292, has broader borrowing powers, including external debt, and a more diversified revenue base, giving it greater fiscal flexibility.

Its debt management is guided by the FRBM Act and parliamentary oversight. State governments, governed by Article 293, primarily borrow domestically and require the Centre's consent if they have outstanding central loans, giving the Centre significant leverage.

States have a more constrained revenue base and are often vulnerable to populist spending pressures and contingent liabilities. Vyyuha's analysis highlights that while the Centre's debt is larger in absolute terms, the fiscal health of states is increasingly critical for overall general government debt sustainability, especially given their rising debt-to-GSDP ratios and interest burdens.

Effective coordination and adherence to fiscal discipline by both tiers of government are essential.

Why it is tested: High-probability Mains question, especially on fiscal federalism, state finances, and the role of the Centre in state debt management.

Questions students ask

10 answered on this topic.

What is the difference between fiscal deficit and public debt?

The fiscal deficit is the difference between the government's total expenditure and its total receipts (excluding borrowings) in a single financial year. It represents the amount of money the government needs to borrow in that year to meet its expenses.

Public debt, on the other hand, is the total accumulated outstanding borrowings of the government over all previous years. Think of it this way: if fiscal deficit is your annual credit card spending, public debt is your total outstanding credit card balance.

A persistent fiscal deficit adds to the public debt. From a UPSC perspective, understanding this distinction is fundamental for analyzing government finances and their long-term implications for the economy.

How does economic growth impact debt sustainability?

Economic growth, particularly nominal GDP growth, is a crucial determinant of debt sustainability. When nominal GDP grows faster than the nominal interest rate on government debt (i.e., g > r), the debt-to-GDP ratio tends to fall, even with a modest primary deficit.

This is often referred to as 'growing out of debt.' Strong economic growth increases government revenues (through higher tax collections) and improves the denominator (GDP) in the debt-to-GDP ratio, making the existing debt stock appear smaller relative to the economy's capacity.

Conversely, slow or negative growth makes it much harder to manage debt, as revenues stagnate and the debt ratio rises, even with fiscal austerity. Vyyuha's analysis highlights that sustained high growth is India's most potent tool for ensuring long-term debt sustainability.

What is the 'snowball effect' in debt dynamics?

The 'snowball effect' refers to a situation where the interest rate on government debt (r) exceeds the nominal GDP growth rate (g). When r > g, the interest payments on existing debt grow faster than the economy's capacity to generate revenue.

This creates a self-reinforcing cycle where debt accumulates even if the government runs a primary balance or a small primary surplus. The debt 'snowballs' or grows on its own, making it increasingly difficult to stabilize or reduce the debt-to-GDP ratio without significant fiscal tightening.

This effect is particularly dangerous for countries with high debt levels and low growth potential. For UPSC, recognizing the 'r-g' differential is key to understanding dynamic debt sustainability.

What role does the primary balance play in debt sustainability?

The primary balance (primary surplus or deficit) is the difference between government revenues and non-interest expenditures. It indicates whether the government is generating enough revenue to cover its current spending, excluding the cost of servicing past debt.

A primary surplus directly contributes to reducing the debt stock, while a primary deficit adds to it. In the debt dynamics equation, the primary balance is a direct policy lever. A government can improve its primary balance by increasing tax revenues, cutting non-essential expenditures, or both.

From a UPSC perspective, achieving a sustainable primary balance is often a core component of any fiscal consolidation strategy aimed at improving debt sustainability.

Why is India's external debt considered less risky than its domestic debt?

While external debt carries exchange rate risk, India's external debt is generally considered less risky than its domestic debt for several reasons. Firstly, a significant portion of India's external debt is long-term and denominated in stable currencies, reducing short-term rollover risk.

Secondly, India maintains comfortable foreign exchange reserves, which act as a buffer against external shocks and provide ample coverage for short-term external debt. Thirdly, the share of external debt in India's total public debt is relatively small compared to domestic debt.

The majority of India's public debt is internal, owed to domestic creditors and denominated in rupees. While domestic debt avoids exchange rate risk, it still carries interest rate and rollover risks, and its sheer size makes it the primary driver of India's overall debt sustainability concerns.

Vyyuha's analysis suggests that while external debt needs monitoring, the focus for India's debt sustainability remains predominantly on domestic fiscal management.

What are 'off-budget borrowings' and why are they a concern for debt sustainability?

Off-budget borrowings refer to loans raised by public sector entities (like public sector undertakings or special purpose vehicles) on behalf of the government, where the principal and/or interest payments are serviced from the government budget, but these borrowings are not explicitly shown as part of the government's direct debt in the budget documents.

They are a concern for debt sustainability because they obscure the true extent of government liabilities. By not being transparently reported, they can lead to an underestimation of the actual debt burden, making fiscal targets appear better than they are.

When these liabilities eventually materialize or require budgetary support, they can suddenly strain public finances. The N.K. Singh Committee and the 15th Finance Commission have both highlighted the need for greater transparency and inclusion of off-budget borrowings in debt calculations to get a realistic picture of a nation's fiscal health.

How do contingent liabilities affect debt sustainability?

Contingent liabilities are potential financial obligations that may arise depending on the outcome of a future event. For governments, these often include guarantees provided to public sector enterprises, state-owned banks, or specific projects, as well as potential costs from natural disasters or legal claims.

They are 'contingent' because they are not direct, immediate debt obligations. However, if the guaranteed entity defaults or the contingent event occurs, the government becomes liable, and these liabilities transform into actual debt.

This can significantly and unexpectedly increase the public debt burden, making it harder to maintain fiscal stability. A robust debt sustainability analysis must therefore account for and monitor contingent liabilities, as they represent a hidden risk to fiscal health.

Vyyuha emphasizes that ignoring these can lead to a sudden and severe fiscal shock.

What is the significance of the 60% debt-to-GDP target for India?

The 60% general government debt-to-GDP target (40% for Centre, 20% for states) was recommended by the N.K. Singh Committee in 2017 as a desirable medium-term goal for India's fiscal health. This target is significant because it provides a benchmark for fiscal prudence and inter-generational equity.

Achieving this ratio would imply a stronger fiscal position, lower interest burden, and greater fiscal space for the government to respond to economic shocks or invest in development. While India's debt-to-GDP ratio surged past this target during the COVID-19 pandemic, the government and the 15th Finance Commission have reiterated the commitment to a glide path towards this or a similar benchmark.

From a UPSC perspective, this target serves as a key reference point for evaluating India's fiscal performance and policy direction.

How does inflation affect debt sustainability?

Inflation has a dual and often complex impact on debt sustainability. On one hand, moderate inflation can erode the real value of outstanding nominal debt, making it easier for the government to repay.

This is sometimes referred to as 'inflation tax' on bondholders. It also boosts nominal GDP, which helps reduce the debt-to-GDP ratio. On the other hand, high or runaway inflation can lead to higher nominal interest rates as lenders demand compensation for the erosion of their money's purchasing power.

This increases the government's interest burden, potentially making debt less sustainable. Moreover, high inflation can destabilize the economy, reduce investor confidence, and make it harder for the government to borrow at reasonable rates.

Vyyuha's analysis suggests that while a little inflation might help, uncontrolled inflation is detrimental to long-term debt sustainability and overall macroeconomic stability.

What are the key differences between static and dynamic debt sustainability measures?

Static debt sustainability measures provide a snapshot of a country's debt position at a specific point in time. The most common example is the debt-to-GDP ratio. While useful, it doesn't tell us whether the current fiscal policies are viable for the future.

Dynamic debt sustainability measures, in contrast, project the debt trajectory into the future, considering how the debt-to-GDP ratio will evolve under various assumptions about economic growth, interest rates, and fiscal policy (primary balance).

These measures use models like the debt dynamics equation and conduct stress tests to assess vulnerabilities. For UPSC, understanding that static measures offer a 'what is' picture, while dynamic measures offer a 'what if' or 'what will be' picture, is crucial for a comprehensive analysis.

Dynamic analysis is more forward-looking and policy-relevant, as it helps identify potential risks before they materialize.