FINC6023 Chap.9 Operational Risk, Stress Testing & Scenario Analysis
Operational Risk, Stress Testing & Scenario Analysis
Operational Risk, Stress Testing and Scenario Analysis covers loss mechanisms that a market VaR number does not describe adequately. Operational risk arises from failed or inadequate people, processes, systems, or external events. The loss may begin with a control failure and then spread through market, credit, liquidity, legal, or reputational channels.
Classifying the initiating cause separately from the financial consequence prevents a scenario from being placed in the wrong family.
Stress testing asks how a portfolio or institution would behave under an extreme but plausible change. It complements VaR because VaR identifies a quantile under a model and does not reveal the depth of loss beyond that cut-off.
A stress test may be historical, prospective, or constructed around portfolio vulnerabilities. Scenario analysis changes several linked variables coherently, whereas a one-factor sensitivity test changes one input and can miss correlations and feedback.
Scenario probabilities can be objective when they are estimated from repeated data or subjective when informed judgement is unavoidable.
Attaching a precise probability to a poorly understood scenario can create false confidence, but avoiding difficult scenarios because their probabilities are uncertain also weakens the exercise.
Governance therefore matters: the scenario should be severe enough to inform decisions, internally consistent, and connected to an action such as a limit, hedge, contingency plan, or capital response.
The available final paper asks why stress testing should supplement VaR. The decisive point is that VaR gives a tail threshold rather than a maximum loss.
Calculation practice should aggregate the gains and losses across every exposed leg under one coherent shock. Written answers should distinguish stress, scenario, and sensitivity analysis, then explain what decision would change if the stress result breaches the institution's tolerance.
What this chapter covers
- 01
Operational risk definition and major loss events (Barings, SocGen, UBS, NAB)
- 02
Why VaR is insufficient: describes 'normal' conditions and only a minimum tail loss
- 03
Stress testing: non-statistical, no probability attached
- 04
Scenario analysis: historical / prospective / portfolio-driven
- 05
Moving one variable at a time ignores correlations (= sensitivity testing)
- 06
Typical shocks: ±100bps yield curve, ±20% equity/vol, ±20bps spreads
- 07
Objective vs subjective probability; the incentive to water down scenarios
Worked example · free
Build a stress scenario and read why it differs from VaR
- 1Equity leg: a 20% fall on $5,000,000 = 0.20 × 5,000,000 = $1,000,000 loss.
- 2Bond leg: ΔP = −D·P·Δy = −4 × 8,000,000 × 0.01 = −$320,000, i.e. a $320,000 loss for a 100bps rise.
- 1Credit leg: 5% of $2,000,000 = $100,000 loss.
- 1Total stress loss = 1,000,000 + 320,000 + 100,000 = $1,420,000.
- 1Explain: this is a deliberately severe, low-probability joint scenario chosen for its damage, whereas the 99% VaR only describes the loss exceeded 1 day in 100 under normal conditions — so a stress loss can be much larger.
Key terms
- Operational risk
- The risk of loss from inadequate or failed internal processes, people, systems, or external events. It excludes strategic and reputational risk and is illustrated by rogue-trader cases (Barings/Leeson, SocGen/Kerviel, UBS/Adoboli).
- Stress testing
- Identifying situations that would cause extraordinary losses, without attaching a probability. It is non-statistical and supplements VaR, which only describes normal conditions and the minimum tail loss.
- Scenario analysis
- Evaluating the portfolio under specified scenarios — historical, prospective or portfolio-driven. Composite VaR can blend stress and historical scenarios by assigning probabilities.
- Objective vs subjective probability
- Objective probabilities are estimated from data (backward-looking); subjective probabilities are judgmental forecasts. Stress and scenario work often relies on subjective probabilities, which invites a regulatory incentive to understate severity.
- Sensitivity analysis
- Sensitivity analysis changes one input while holding others fixed, which isolates a local exposure but can miss correlated moves and feedback captured by a scenario.
- Prospective scenario
- A prospective scenario is a forward-looking, internally coherent set of shocks designed to reveal vulnerabilities that may not appear in the historical record.
Operational Risk, Stress Testing & Scenario Analysis FAQ
Why isn't VaR enough on its own?
VaR describes only 'normal' market conditions and reports the MINIMUM loss in the tail (the quantile), not how deep the tail goes. It cannot capture rare, joint, extreme events. Stress testing and scenario analysis fill that gap by deliberately examining severe situations VaR was never designed to see.
What is the difference between scenario analysis and sensitivity testing?
Scenario analysis shocks several variables together in a coherent economic story, such as a recession with falling equity prices and wider credit spreads. Sensitivity testing moves one variable at a time, which isolates an exposure but ignores correlations and feedback between factors. Moving variables separately can understate the joint damage of a real crisis.
Is a probability attached to a stress test?
No — pure stress testing is non-statistical and attaches no probability; it simply asks how bad the loss would be if a scenario occurred. Composite approaches can later weight scenarios by subjective probabilities, but the core stress test is judgment-driven, not distributional.
How does the final connect stress testing and VaR?
The available paper asks why stress testing should supplement VaR. VaR identifies a loss threshold at a selected confidence under a model, but it does not state how large losses become beyond that threshold. Stress testing supplies severe, coherent outcomes and reveals concentrations or feedback that the ordinary model may omit.
What makes a useful stress scenario?
A useful scenario is severe enough to challenge the portfolio, plausible enough to inform decisions, internally consistent across risk factors, and linked to an action. It should specify the transmission mechanism, not merely list large shocks. The result should lead to a limit, hedge, capital, liquidity, or contingency response.
Exam move
Begin with the operational-risk definition and classify the initiating failure before describing the resulting financial losses. For each case, write four fields: failed person, process, system, or external event; immediate loss; secondary risk channels; and the control that could have interrupted the chain. For stress testing, build scenarios from linked variables rather than isolated shocks.
State why the scenario is plausible, calculate the impact on every relevant position, and connect the result to a management response. Practise the conceptual contrast that the final paper uses: VaR gives a model-based tail threshold, while stress testing explores the scale and transmission of losses outside ordinary conditions. Keep sensitivity analysis separate because it changes one factor while holding others fixed.
When a probability is requested, label whether it is data-based or judgemental and avoid spurious precision. Finish each practice response with the limit, hedge, liquidity buffer, or contingency action supported by the analysis.
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