Mean reversion · daily rule · Software & devices
Bollinger Reversion on CrowdStrike
What the play says
CRWD with the play, last two years
Shading shows the play's call from the close that triggered it.
Growth of $10,000 since 2019
Log scale. After trading costs, with T-bill interest while out.
The record
The play against buying and holding CRWD over exactly the same dates, after costs.
| Play, since 2019 | Hold, since 2019 | Play, 5 yrs | Hold, 5 yrs | |
|---|---|---|---|---|
| Annual return | −0.5% | +45.0% | −6.3% | +31.2% |
| Total return | −4% | +1,374% | −28% | +286% |
| Worst drawdown | −56.6% | −67.7% | −56.6% | −67.7% |
| Volatility | 30.9% | 55.7% | 27.8% | 52.6% |
| Sharpe ratio | 0.05 | 0.90 | −0.23 | 0.71 |
| Time invested | 20% | 100% | ||
| Switches per year | 6.6 | 0 |
Every call, graded
Right on 25 of 48 closed calls (52%). In calls averaged −0.1%; out calls saw CRWD move +13.8% on average.
| Called | Call | Price | Until | CRWD moved | Result |
|---|---|---|---|---|---|
| Apr 7, 2026 | OUT | $105.81 | now | +146.9% | open |
| Mar 27, 2026 | IN | $92.39 | Apr 7, 2026 | +14.5% | ✓ right |
| Mar 4, 2026 | OUT | $101.92 | Mar 27, 2026 | −9.3% | ✓ right |
| Feb 3, 2026 | IN | $105.43 | Mar 4, 2026 | −3.3% | ✕ wrong |
| Jan 26, 2026 | OUT | $117.08 | Feb 3, 2026 | −9.9% | ✓ right |
| Dec 15, 2025 | IN | $121.87 | Jan 26, 2026 | −3.9% | ✕ wrong |
| Dec 3, 2025 | OUT | $131.04 | Dec 15, 2025 | −7.0% | ✓ right |
| Nov 20, 2025 | IN | $125.33 | Dec 3, 2025 | +4.6% | ✓ right |
| Aug 28, 2025 | OUT | $110.50 | Nov 20, 2025 | +13.4% | ✕ wrong |
| Aug 7, 2025 | IN | $106.25 | Aug 28, 2025 | +4.0% | ✓ right |
| Mar 19, 2025 | OUT | $93.76 | Aug 7, 2025 | +13.3% | ✕ wrong |
| Mar 6, 2025 | IN | $86.93 | Mar 19, 2025 | +7.9% | ✓ right |
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 49 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.