IMF Survey: What Is a Bank Stress Test?

IMF News, July 29, 2010

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Date: July 29, 2010
Stress tests subject banks to “unlikely but plausible” scenarios to determine whether an institution has enough net wealth—capital—to weather adverse developments.
Primary aims:
- Find weak spots in the banking system at an early stage.
- Guide preventive actions by banks and those charged with their oversight.
Results depend on the assumptions’ pessimism and must be interpreted in light of those assumptions.

Performed by:
- Banks themselves for internal risk management.
- Supervisors as part of oversight of individual banks and banking systems.
- International organizations (e.g., IMF) to assess banking systems’ resilience; virtually all Fund Financial System Stability Assessment reports include stress tests.
Common focus areas across most stress tests:
- Credit risk
- Market risk
- Liquidity risk

Credit risk:
- Reflects potential losses from defaults on loans (consumer loans, mortgages, corporate loans).
- Stress tests examine impact of rising loan defaults or non-performing loans on bank profit and capital.
Market risk:
- Gauges how changes in exchange rates, interest rates, and prices of financial assets (equities, bonds) affect asset values, profits, and capital.
- Typically assumes a drop in asset values in the bank’s portfolio.
Macro stress tests:
- Link changes in asset prices and default rates to a negative economic scenario (e.g., unemployment climbs, economic growth plummets).
- Benefit: communicate underlying assumptions more clearly.
- Downside: scenarios harder to build; results subject to modeling uncertainty because there is no standard way to link economic assumptions to default rates or asset prices.
Recent practice:
- The United States and European authorities used macro stress-test approaches in their recent stress tests.

Pre-2008 view:
- Supervisors paid less attention to liquidity; healthy, solvent banks were expected to manage cash flows or access funding by borrowing or selling assets.
- Deposit insurance seen as a buffer against runs for fundamentally healthy banks.
Crisis lessons:
- Liquidity shocks in 2008 were more widespread and severe than anticipated.
- Non-bank liquidity providers (e.g., money market funds) stopped lending, exacerbating shortages.
- Many banks were unable to borrow at reasonable rates or sell assets at acceptable prices as asset prices collapsed.
- Authorities resorted to unorthodox, massive cash injections into liquidity-strapped institutions.
Pre-crisis liquidity stress tests:
- Focused on deposit withdrawals or inability to refinance (e.g., triggered by credit downgrade).
- Proven insufficient to simulate the range of potential liquidity shortages.
Post-crisis developments:
- Intensified efforts to develop more adequate liquidity tools.
- The Basel committee is focusing on liquidity risk and debating multiple proposals.

Scope expansion:
- Stress tests are being expanded beyond individual risks to system-wide risks.
Key modeling objectives:
- Identify connections between individual financial institutions and propagation channels that can threaten overall financial stability.
- Account for the global scale of banks’ operations and potential cross-border transmission of shocks (examples cited: foreign exchange funding, structured credit, credit derivatives markets).
- Assess interplay between the financial sector and economic stability, including feedback loops where economic shocks affect financial institutions’ asset portfolios and institution distress affects the economy.
Ongoing efforts:
- National supervisors and international organizations (IMF, Bank for International Settlements) are developing new risk-modeling techniques and stress test methodologies.
- Sophisticated approaches are needed to examine both the impact of economic shocks on financial institutions and the subsequent macroeconomic effects.

Stress tests help spot emerging risks but are sensitive to scenario design and modeling assumptions.
Macro stress tests improve transparency of assumptions but increase modeling complexity and uncertainty.
Liquidity risk requires broader and more realistic testing than pre-crisis frameworks provided.
Systemic and cross-border linkages must be incorporated into next-generation stress-testing methodologies.
Banks, regulators, and supervisors will continue to develop stress tests as tools for identifying emerging risks; financial markets will monitor results closely.

IMF Survey: What Is a Bank Stress Test? — July 29, 2010