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Forecast vs scenario analysis
What is the difference between a forecast and a scenario?
Short answer
A forecast is the model's estimate given current conditions. A scenario is a calculation of what would happen if assumptions you supply turned out to be true. A scenario makes no claim that those assumptions are likely.
- Author:
- NeoInvest team
- Reviewer:
- Review pending
- Published:
- 2026-07-19
- Last reviewed:
- 2026-07-19
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Different questions entirely
A forecast answers: given everything the model can currently see, what movement does it estimate over this horizon? A scenario answers a question you posed: if US equities fell 8% and sterling strengthened 5% against the dollar, what would that mean for this portfolio? The first is an estimate about the world. The second is arithmetic about a hypothesis.
Where the numbers come from
Forecast figures come from a model with a version, a generation time and an expiry. Scenario figures come from deterministic calculation over assumptions you set — run the same scenario twice and you get the same answer, because nothing is being estimated. That difference in provenance is why the two are presented separately and never blended into one number.
Why the distinction matters
Treating a scenario result as a prediction is how a stress test turns into a reason to act. Someone who runs a severe scenario, sees a large negative figure and reads it as what the product expects to happen has misread it entirely — the figure describes their own assumption, not a view about the market. This is why every scenario result carries the assumptions that produced it alongside the number.
Using them together
They complement each other. A forecast tells you what current conditions suggest. A scenario lets you ask what would happen under conditions that are not currently expected — which is precisely what makes it useful for understanding concentration and exposure, where the risk is in the outcome you have not planned for.
Common misunderstandings
Not quite: A scenario result is a prediction of what will happen.
It is the calculated consequence of an assumption you chose. The engine takes no view on whether that assumption is plausible.
Not quite: A worse scenario result means a worse portfolio.
It means the portfolio is more sensitive to that particular assumption. Sensitivity to one scenario is not a general quality judgement.
Not quite: Scenarios and forecasts should agree.
There is no reason they would. They answer different questions from different inputs.
Limitations
- A scenario applies your stated assumptions only; real market moves arrive with correlated effects a simple assumption does not capture.
- Results depend entirely on the accuracy of the portfolio data supplied.
- Historical relationships used in the calculation may not hold in future conditions.
Sources and further reading
Educational information only. This article does not constitute investment, tax or legal advice, and does not take your circumstances into account.