Forex glossary
Black Swan Event
A black swan describes an exceptional, high-impact event outside the expectations used by an observer or model. In markets it can reveal gaps in risk assumptions and liquidity; neither VaR nor CVaR guarantees coverage of scenarios omitted from a model.
Illustrative example
How does it work in practice?
Suppose a hypothetical stress model assumes a worst decline of 5%, but an unexpected announcement produces a 12% gap. The model omitted that scenario, so its assumed bound does not cap the actual loss.
A case to work through
Scenarios without outages
Model: a test varies prices but always assumes platform access and the ability to close positions.
- Identify assumptions shared by every scenario.
- Without an outage scenario, access risk remains outside the test.
What follows? Add a question about lost access before calling the test complete.
Example boundary: Not every outage is a black swan; the label depends on prior expectations.
A useful distinction
Black Swan Event / Tail Risk
Tail risk concerns extreme distribution outcomes; a black swan can reveal events outside the assumed model.
Check your understanding
Identify a risk omitted from a scenario set.
Show the answer and explanation
They test prices but omit loss of access
Scenario count does not remove a shared omission.
From position budgets to portfolios
Step 11 / 11 · 0 / 11 reviewed
View the full sequence →Progress is saved only in this browser.
Read the fuller explanation
Related terms
Sources and documentation
- BIS MAR10: market risk terminology
VaR at a stated horizon/confidence and expected shortfall as a tail mean.
Document read:
The example illustrates the mechanism. Check current account conditions and instrument specifications with the provider.