Mean reversion · daily rule · Media & telecom
Bollinger Reversion on T-Mobile US
What the play says
TMUS with the play, last two years
Shading shows the play's call from the close that triggered it.
Growth of $10,000 since 2007
Log scale. After trading costs, with T-bill interest while out.
The record
The play against buying and holding TMUS over exactly the same dates, after costs.
| Play, since 2007 | Hold, since 2007 | Play, 5 yrs | Hold, 5 yrs | |
|---|---|---|---|---|
| Annual return | +6.3% | +5.2% | +14.2% | +6.8% |
| Total return | +230% | +168% | +94% | +39% |
| Worst drawdown | −58.9% | −86.3% | −17.3% | −44.0% |
| Volatility | 22.4% | 39.9% | 13.5% | 26.1% |
| Sharpe ratio | 0.33 | 0.29 | 0.77 | 0.24 |
| Time invested | 22% | 100% | ||
| Switches per year | 8.8 | 0 |
Every call, graded
Right on 109 of 171 closed calls (64%). In calls averaged +1.7%; out calls saw TMUS move +1.3% on average.
| Called | Call | Price | Until | TMUS moved | Result |
|---|---|---|---|---|---|
| Oct 9, 2026 | IN | $148.58 | now | +3.5% | open |
| Oct 8, 2026 | OUT | $171.31 | Oct 9, 2026 | −13.3% | ✓ right |
| Sep 17, 2026 | IN | $166.45 | Oct 8, 2026 | +2.9% | ✓ right |
| Jul 6, 2026 | OUT | $180.75 | Sep 17, 2026 | −7.9% | ✓ right |
| Jun 29, 2026 | IN | $172.97 | Jul 6, 2026 | +4.5% | ✓ right |
| Jun 12, 2026 | OUT | $188.01 | Jun 29, 2026 | −8.0% | ✓ right |
| Jun 3, 2026 | IN | $180.41 | Jun 12, 2026 | +4.2% | ✓ right |
| Apr 29, 2026 | OUT | $195.97 | Jun 3, 2026 | −7.9% | ✓ right |
| Mar 18, 2026 | IN | $204.33 | Apr 29, 2026 | −4.1% | ✕ wrong |
| Jan 30, 2026 | OUT | $194.09 | Mar 18, 2026 | +5.3% | ✕ wrong |
| Jan 13, 2026 | IN | $186.67 | Jan 30, 2026 | +4.0% | ✓ right |
| Dec 29, 2025 | OUT | $199.93 | Jan 13, 2026 | −6.6% | ✓ 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 172 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.