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Finaxion Research · Upper Bollinger band breakout · single stocks · Recomputed 2026-09-10

Does Upper Bollinger band breakout work on GRMN?

Upper Bollinger band breakout does not beat buy-and-hold on GRMN: -21.5 points a year over 26 years.

Total return
-70.7%
Buy and hold
×55
CAGR
-4.7%
Sharpe
-0.81
Max drawdown
-84.4%
Trades
456
Out of sample
overfit
Years
26
1×10×2001200320052007200920112013201520172019202120232025
StrategyGRMN

Findings

  1. Upper Bollinger band breakout does not beat buy-and-hold on GRMN: -21.5 points a year over 26 years.
  2. Against the S&P 500 over the same window: -13.6 points a year.
  3. Total return -70.7% versus ×55 for buy-and-hold, with 456 trades.
  4. The result does not hold out of sample: it is overfit.
  5. Maximum drawdown -84.4%.
  6. It beats in neither half of the history (split at 2013).
  7. It ranks #146 of 235 markets for this strategy by annual excess over the S&P 500.

Findings derived from the full panel. Each carries its number and its denominator; the computations are reproducible with artifact 0a2f2c1b7ca1.

Exactly what was tested

Long while the close is above the upper band (20, 2σ); flat when it drops back below.

How to read it

The verdict compares the strategy with buying and holding GRMN over the same window, with round-trip costs per asset class. “Out of sample” is walk-forward: the rule is fit on one stretch and judged on the next. A result that beats in the full sample but not out of it is overfit. Full methodology in the protocol. How we test.

Open this backtest with its trades   Trades (CSV)

Every strategy on GRMN → · Full page for Upper Bollinger band breakout →

How to cite

Finaxion Research (2026). Does Upper Bollinger band breakout work on GRMN?. Daily backtest 1962-01-01–2026-08-31, artifact 0a2f2c1b7ca1. https://finaxion.app/en/research/bollinger-breakout/grmn

Not a recommendation. Past performance does not guarantee future results.