Mean reversion · daily rule · Software & devices
Bollinger Reversion on Descartes Systems
What the play says
DSG with the play, last two years
Shading shows the play's call from the close that triggered it.
Growth of C$10,000 since 2005
Log scale. After trading costs, with T-bill interest while out.
The record
The play against buying and holding DSG over exactly the same dates, after costs.
| Play, since 2005 | Hold, since 2005 | Play, 5 yrs | Hold, 5 yrs | |
|---|---|---|---|---|
| Annual return | +14.0% | +20.4% | +19.6% | +3.1% |
| Total return | +1,614% | +5,519% | +144% | +16% |
| Worst drawdown | −29.4% | −50.9% | −29.4% | −50.9% |
| Volatility | 16.2% | 31.0% | 16.4% | 31.3% |
| Sharpe ratio | 0.78 | 0.70 | 0.94 | 0.13 |
| Time invested | 20% | 100% | ||
| Switches per year | 9.9 | 0 |
Every call, graded
Right on 148 of 214 closed calls (69%). In calls averaged +2.6%; out calls saw DSG move +2.2% on average.
| Called | Call | Price | Until | DSG moved | Result |
|---|---|---|---|---|---|
| Sep 14, 2026 | OUT | C$111.16 | now | +8.7% | open |
| Sep 9, 2026 | IN | C$101.44 | Sep 14, 2026 | +9.6% | ✓ right |
| Jul 28, 2026 | OUT | C$106.62 | Sep 9, 2026 | −4.9% | ✓ right |
| Jul 23, 2026 | IN | C$92.67 | Jul 28, 2026 | +15.1% | ✓ right |
| May 20, 2026 | OUT | C$99.65 | Jul 23, 2026 | −7.0% | ✓ right |
| May 12, 2026 | IN | C$92.11 | May 20, 2026 | +8.2% | ✓ right |
| Apr 15, 2026 | OUT | C$99.70 | May 12, 2026 | −7.6% | ✓ right |
| Apr 8, 2026 | IN | C$93.08 | Apr 15, 2026 | +7.1% | ✓ right |
| Feb 26, 2026 | OUT | C$92.84 | Apr 8, 2026 | +0.3% | ✕ wrong |
| Jan 21, 2026 | IN | C$113.05 | Feb 26, 2026 | −17.9% | ✕ wrong |
| Dec 3, 2025 | OUT | C$115.81 | Jan 21, 2026 | −2.4% | ✓ right |
| Oct 29, 2025 | IN | C$125.14 | Dec 3, 2025 | −7.5% | ✕ wrong |
An in call is right when the price rose before the next call; an out call is right when it fell. The latest 12 of 215 calls shown.
How the play works
- In on a close below the lower band (20-day average − 2 standard deviations).
- Out on a close above the 20-day average.
This runs against Bollinger's advice that tags of the bands are not signals. It is shown because so many traders use it.
The case against
Valeriy Zakamulin tested moving-average timing on up to 155 years of U.S. stock data and found no statistically significant edge in the second half of that record. The rules earned their keep in a few severe bear markets and lagged buy and hold for long stretches in between.