Mean reversion · daily rule · Sectors
Bollinger Reversion on Health Care Select Sector ETF
What the play says
XLV with the play, last two years
Shading shows the play's call from the close that triggered it.
Growth of $10,000 since 2005
Log scale. After trading costs, with T-bill interest while out.
The record
The play against buying and holding XLV over exactly the same dates, after costs.
| Play, since 2005 | Hold, since 2005 | Play, 5 yrs | Hold, 5 yrs | |
|---|---|---|---|---|
| Annual return | +4.8% | +10.2% | +8.7% | +8.0% |
| Total return | +178% | +721% | +52% | +47% |
| Worst drawdown | −27.2% | −39.2% | −6.8% | −17.1% |
| Volatility | 10.9% | 16.7% | 7.5% | 15.2% |
| Sharpe ratio | 0.32 | 0.56 | 0.64 | 0.33 |
| Time invested | 19% | 100% | ||
| Switches per year | 8.6 | 0 |
Every call, graded
Right on 117 of 186 closed calls (63%). In calls averaged +0.9%; out calls saw XLV move +1.4% on average.
| Called | Call | Price | Until | XLV moved | Result |
|---|---|---|---|---|---|
| May 12, 2026 | OUT | $144.66 | now | +17.3% | open |
| Apr 27, 2026 | IN | $142.29 | May 12, 2026 | +1.7% | ✓ right |
| Apr 8, 2026 | OUT | $148.44 | Apr 27, 2026 | −4.1% | ✓ right |
| Mar 5, 2026 | IN | $152.03 | Apr 8, 2026 | −2.4% | ✕ wrong |
| Sep 30, 2025 | OUT | $136.88 | Mar 5, 2026 | +11.1% | ✕ wrong |
| Sep 25, 2025 | IN | $131.93 | Sep 30, 2025 | +3.8% | ✓ right |
| Aug 13, 2025 | OUT | $130.50 | Sep 25, 2025 | +1.1% | ✕ wrong |
| Jul 31, 2025 | IN | $127.70 | Aug 13, 2025 | +2.2% | ✓ right |
| Jul 23, 2025 | OUT | $133.42 | Jul 31, 2025 | −4.3% | ✓ right |
| Jul 21, 2025 | IN | $128.35 | Jul 23, 2025 | +4.0% | ✓ right |
| Jun 3, 2025 | OUT | $129.63 | Jul 21, 2025 | −1.0% | ✓ right |
| May 14, 2025 | IN | $125.48 | Jun 3, 2025 | +3.3% | ✓ 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 187 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.