Mean reversion · daily rule · Software & devices
Bollinger Reversion on GoPro
What the play says
GPRO with the play, last two years
Shading shows the play's call from the close that triggered it.
Growth of $10,000 since 2014
Log scale. After trading costs, with T-bill interest while out.
The record
The play against buying and holding GPRO over exactly the same dates, after costs.
| Play, since 2014 | Hold, since 2014 | Play, 5 yrs | Hold, 5 yrs | |
|---|---|---|---|---|
| Annual return | −12.3% | −25.4% | −5.9% | −33.4% |
| Total return | −80% | −97% | −26% | −87% |
| Worst drawdown | −92.5% | −99.5% | −60.5% | −95.9% |
| Volatility | 38.2% | 71.5% | 41.3% | 80.8% |
| Sharpe ratio | −0.21 | −0.09 | −0.04 | −0.17 |
| Time invested | 33% | 100% | ||
| Switches per year | 9.6 | 0 |
Every call, graded
Right on 74 of 117 closed calls (63%). In calls averaged −1.6%; out calls saw GPRO move +0.5% on average.
| Called | Call | Price | Until | GPRO moved | Result |
|---|---|---|---|---|---|
| Oct 7, 2026 | IN | $1.22 | now | −3.3% | open |
| Aug 31, 2026 | OUT | $0.876 | Oct 7, 2026 | +39.3% | ✕ wrong |
| Aug 11, 2026 | IN | $0.620 | Aug 31, 2026 | +41.3% | ✓ right |
| Jul 22, 2026 | OUT | $0.739 | Aug 11, 2026 | −16.1% | ✓ right |
| Jul 17, 2026 | IN | $0.660 | Jul 22, 2026 | +12.0% | ✓ right |
| Jul 9, 2026 | OUT | $0.760 | Jul 17, 2026 | −13.2% | ✓ right |
| Jun 10, 2026 | IN | $0.790 | Jul 9, 2026 | −3.8% | ✕ wrong |
| Feb 27, 2026 | OUT | $0.968 | Jun 10, 2026 | −18.4% | ✓ right |
| Jan 20, 2026 | IN | $1.29 | Feb 27, 2026 | −25.0% | ✕ wrong |
| Nov 28, 2025 | OUT | $1.63 | Jan 20, 2026 | −20.9% | ✓ right |
| Nov 3, 2025 | IN | $1.84 | Nov 28, 2025 | −11.4% | ✕ wrong |
| Apr 24, 2025 | OUT | $0.643 | Nov 3, 2025 | +186.2% | ✕ 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 118 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.