Inconceivable: A Practical Guide to Tail-Risk Scenario Design
As risk professionals, we excel at modeling the probable and the plausible, but can struggle when confronted with scenarios that go beyond our historical framework. The past few years have delivered a sobering reminder of this blind spot.
The Global Financial Crisis and the 2020 pandemic shutdown were not just improbable events: they exceeded the imaginations of most risk managers. Even a foreseeable event, such as the rapid rise in interest rates in 2022, was not anticipated by many institutions, despite extensive monetary policy history. Every crisis teaches us the same uncomfortable truth: the greatest losses often emerge from scenarios we deem too unlikely to prepare for.
Traditional scenario analysis works well for routine business-as-usual planning and stress testing, but may be inadequate for true tail events. Our challenge goes beyond imagining extreme risks. The real value we provide is developing actionable frameworks and models for events that defy typical probability distributions. In short, how do we design scenario planning for the unthinkable?
Start with What Could Break
Most scenario design begins with historical analysis. That is, we extend past patterns incrementally into plausible futures. This approach may work for general stress testing, but misses the mark for tail risks. By definition, genuine tail events have no meaningful historical precedent.
[....]
