Concept
Why Short Date Ranges Mislead
Short windows often capture only one chapter of the story, so they can exaggerate luck in either direction. Test longer and overlapping windows to see whether a result holds up.
Published: December 26, 2025 · Updated: December 26, 2025 · By FinToolSuite Editorial
Disclaimer
- Educational purposes only, not financial advice.
- Examples are illustrative and simplified.
- Past performance is not a reliable indicator of future results.
- Market returns can be negative.
- See the Privacy Policy for data handling details.
Open the Investment History Checker
Run short and longer windows to see how the story changes.
Quick answer
- Short windows can overstate returns or losses.
- They can hide the worst peak to trough drop.
- Sanity check with longer and overlapping windows.
Reason 1: Lucky or unlucky slice
Starting after a crash can make returns look unusually high; starting near a peak can make returns look unusually low. Short windows capture only a slice of the cycle.
Reason 2: Drawdowns can be hidden
A short window might end before the worst drop or start after it, so you may never see the deepest drawdown in that slice.
See max drawdown explained for context.
Reason 3: Recovery time is hidden
A return number doesn’t show how long it took to recover. Deep drops can take years to climb back; short windows can skip that recovery.
Illustrative example
| Window | Start level | Lowest level | End level | What it looks like |
|---|---|---|---|---|
| 1 year | 100 | 80 | 120 | Looks great, dip hidden |
| 5 years | 100 | 60 | 140 | Shows dip and recovery |
| 10 years | 100 | 50 | 200 | Multiple cycles visible |
Illustrative only; actual results depend on the path.
A safer sanity check method
- Run your short window and save it.
- Extend the start date earlier and rerun.
- Extend the end date later if possible and rerun.
- Compare CAGR and max drawdown together.
- Check best and worst years and negative years if shown.
Read choosing start and end dates for more detail.
Common misreads to avoid
- Thinking the short window predicts the next year.
- Comparing two tickers using different windows.
- Focusing only on total return.
- Ignoring drawdown because the ending value is positive.
See more pitfalls in common mistakes.
Quick checklist
- [ ] Tested at least one longer window
- [ ] Checked max drawdown alongside return
- [ ] Scanned the yearly table for concentration
- [ ] Avoided comparing different windows across tickers
FAQ preview
How short is too short?
Short windows are noisy. Test longer ranges to see if results persist.
Why does shifting my start date change results so much?
Small shifts can move you from a peak to a dip, changing returns and drawdowns.
Can a short window ever be useful?
It can show recent moves, but pair it with longer windows for context.
Where do I see drawdown?
Check max drawdown and the chart for the worst peak-to-trough drop.
Should I always test multiple windows?
Yes. Multiple windows help reduce cherry picking.
Test more than one window
Run short and long ranges, compare drawdowns and yearly patterns, and export for review.