Range of outcomes
Instead of a single number, the spread of possible results: the pessimistic, typical and optimistic cases.
Nobody knows what an investment will be worth in 20 years. The honest thing is to show a range: what would happen in a bad case, a typical one and a good one.
For example, $100 a month in the S&P 500 for 20 years ($24,000 put in overall), with the risk its history shows: the pessimistic case ends at $37,113, the typical one at $81,332 and the optimistic one at $179,987.
The range isn't a limit: things can turn out worse than the pessimistic case or better than the optimistic one. One case in ten ends below the pessimistic one.
They're percentiles of thousands of simulated paths: P10 (10% end below it), P50 (the median) and P90 (10% end above it). The shaded area on the chart goes from P10 to P90 at each date.
The band isn't a path: at each date, all the paths are sorted and the percentiles are taken separately.
At Compass, the paths come from a block bootstrap of real history (2,000 paths, one-year blocks). For the S&P 500 the growth is the historical one; in the Simulator you can choose another.
- From pessimistic to optimistic
- Typical
- Put in
2,000 paths built from S&P 500 history since 1926.
Where you see it in Compass
- Simulator · Look aheadIn Look ahead, the pessimistic, typical and optimistic cases for your plan.
Related terms
Frequently asked questions
What do P10, P50 and P90 mean?
They're percentiles: P10 is the result that only 10% of cases fail to reach, P50 is the middle one and P90 is the one only 10% exceed.
Is the pessimistic case the worst that can happen?
No. One case in ten ends below it. It's a bad case, not the worst possible one.
Calculated and reviewed by Compass. Sources, checks and method
Figures with data as of October 26, 2026. Educational content. Not financial advice. Past results don't guarantee future results.