Bollinger Bands

Bollinger Bands wrap a moving average in an envelope set a certain number of standard deviations above and below it — a way of showing whether price is unusually high or low relative to its own recent range.

In 30 Seconds

• Bollinger Bands are a moving average plus an envelope set some standard deviations above and below it.
• They measure relative position — is price high or low versus its own recent volatility-scaled range?
• Touching the upper band is NOT a sell signal — in strong trends price "walks the band." That's the key myth.
• The bands widen and narrow with volatility — squeezes (narrow) signal low volatility, not direction.

Definition

Bollinger Bands, developed by John Bollinger in the 1980s, have three components:

1. Middle band — a moving average of price (commonly a 20-period simple moving average).
2. Upper band — the middle band plus a number of standard deviations of price (commonly two).
3. Lower band — the middle band minus that same number of standard deviations.

Because standard deviation *is* a measure of volatility, the bands automatically adapt: in calm markets they contract, in volatile markets they expand. This is what makes them different from fixed-width channels — they breathe with the market.

Price near the upper band means it's high relative to its recent volatility-adjusted range; near the lower band, low. Around 90%+ of price action typically stays within the bands (by construction, since two standard deviations captures most of a distribution) — which is exactly why band *touches* are normal events, not rare signals.

"Bollinger Bands show relative position within recent volatility — not a boundary price "shouldn't" cross."

Why It Matters

Bollinger Bands are popular because they answer a genuinely useful question: "is price high or low *relative to its own recent behavior*?" — adjusting automatically for how volatile the market is. That's more informative than a fixed level, because "high" in a calm market and "high" in a wild one are very different.

But their popularity also breeds the biggest mistake: treating a band touch as a reversal signal. "Price hit the upper band, time to sell" ignores that in a strong uptrend, price *rides* the upper band — touching or hugging it repeatedly while climbing. Selling every upper-band touch means fighting strong trends. The bands describe *position*, and position at an extreme is common during trends, not a reversal countdown.

The useful, honest use is as a *volatility-scaled description* of where price sits — a condition to study, not a signal to obey.

How It Works (a simple example)

Picture a quiet market: price drifts in a tight range, so its standard deviation is small, and the bands sit close together — a "squeeze." Then news hits and price moves sharply. Volatility jumps, standard deviation expands, and the bands widen dramatically.

Notice what the squeeze did and didn't tell you: a narrow-band squeeze signals that volatility is *low* and often precedes a volatility *expansion* — but it says nothing about *which direction* the expansion will go. And when price then pushes to the upper band, that reflects a strong up-move relative to recent range — which, in a genuine trend, can persist bar after bar.

How MPM Uses Bollinger Bands

MPM expresses band position as an objective, disclosed condition rather than a subjective "near the band" judgment:

• Position is mapped to a defined scale. Rather than eyeballing whether price is "at" a band, HIE maps band position to an objective value so "at the upper band" means the same thing every time.
• Direction stays context-only. A band-position condition is reported against the base rate — what historically followed — never as a buy or sell.

HIE maps band position so that +1 = exactly the upper band and −1 = exactly the lower band (values beyond ±1 mean price is outside the bands). The bands are built on a 20-period simple moving average with a 2-standard-deviation multiple (using the sample standard deviation). When you ask about a band condition, the "What ran" line shows the position value directly — for example:

'at the upper Bollinger band' → Bollinger position above 1

So "at the band" is an exact, disclosed number rather than a subjective call.

Interpretation

• Price near the upper band — high relative to recent volatility-scaled range; common in uptrends, NOT a reversal signal.
• Price near the lower band — low relative to that range; common in downtrends, NOT a bounce signal.
• Bands narrowing (squeeze) — volatility is contracting; often precedes expansion, but says nothing about direction.
• Bands widening — volatility is expanding; the move driving it can be up or down.

The honest reading: band position tells you where price sits within its recent volatility, and band width tells you about volatility itself. Neither tells you direction — that's a separate question MPM answers with history, not with the bands.

Common Mistakes

"Price hit the upper band — sell."

The classic error. In strong trends price walks the band. A touch is a position description, not a reversal signal.

"A squeeze means price will go up."

A squeeze signals low volatility and often precedes expansion — but gives no directional information. Reading direction into a squeeze is inventing information that isn't there.

"Price can't go outside the bands."

It can and does. The bands capture most action by construction, but breakouts beyond them happen — often at the start of strong moves.

What It Is Not

• Not a reversal signal. Band touches are common, especially in trends.
• Not a directional indicator. Squeezes and band width describe volatility, not direction.
• Not a hard boundary. Price trades outside the bands regularly.

Limitations

Bollinger Bands are built from a moving average and standard deviation, so they inherit the lag of both — they describe recent, past behavior and adapt only as new data arrives. Their settings (period, standard-deviation multiple) change their sensitivity, and there's nothing universal about the common defaults. Most importantly, the bands describe *position and volatility*, never direction — the single most common misuse is reading directional signals into what is fundamentally a volatility-scaled position measure.

How This Fits Into MPM

Bollinger Bands fit MPM's approach to indicators: take a popular, widely-misread tool, define its condition objectively (a disclosed band-position mapping), and report what history actually did afterward instead of turning a band touch into a signal.