Definition
Scenario analysis is an analytical technique that constructs specific coherent combinations of inputs representing alternative future conditions and reports the model's output under each combination.
Why it matters
Real futures do not arrive one variable at a time. When interest rates fall, credit spreads typically widen and equity returns move in ways that reflect the same underlying condition. Scenario analysis handles related inputs jointly by defining internally consistent combinations (a low-rate scenario, a high-inflation scenario, a stagnation scenario) and comparing outputs across them, which produces a more realistic picture of what specific future conditions would mean for the arrangement being analyzed than one-variable-at-a-time sensitivity output can.
How it works
A scenario analysis defines a small number of internally consistent input combinations, each representing a coherent alternative future. Each scenario specifies values for all relevant inputs (return, inflation, mortality experience, insurer solvency where relevant) that hang together economically, then runs the model under each combination and reports the output. Consider a retirement projection with three scenarios for the next 20 years: a base scenario (5 percent nominal returns, 2.5 percent inflation), a stagflation scenario (3 percent nominal returns, 5 percent inflation), and a strong-growth scenario (8 percent nominal returns, 2 percent inflation). The projection under each scenario produces a specific balance path and a specific real income path, and the comparison across scenarios reveals which scenario the arrangement is most exposed to. Scenario analysis differs from sensitivity analysis in treating inputs as jointly determined rather than varying one at a time; it differs from stochastic modeling in specifying discrete named scenarios rather than sampling from distributions. Scenarios are analytical constructions, not forecasts; the value is in the structural comparison across scenarios, not in any specific scenario's status as prediction.
In practice
An individual comparing retirement arrangements benefits from asking how each arrangement performs under a small set of clearly defined scenarios rather than relying on a single central projection. A scenario in which real interest rates fall by two percentage points is a coherent alternative future that changes the relative economics of solo drawdown, SPIA, and pooled arrangements in specific ways. The individual should ask the professional producing the analysis to disclose which scenarios are being compared and why those particular scenarios were selected. Well-constructed scenarios illuminate the structural differences between arrangements; poorly constructed scenarios (too many, too similar, not internally consistent) obscure them.
Related terms
- Sensitivity analysis
- Stress testing
- Deterministic modeling
- Monte Carlo simulation
- Stochastic modeling
- Cost of income
- Realized value
- Insurer load