Island Reversals

Core idea

An island reversal is a stretch of price action isolated from the surrounding chart by two gaps at approximately the same price level. The first gap separates the "island" from the prior trend; the second gap, in the opposite direction, separates it from the new trend. Visually striking — but statistically dreadful.

Bulkowski's data ranks island bottoms last for failure rate in bear markets and next-to-last in bull markets. Island tops are also near the bottom of the bearish performance list. The pattern is easy to identify and easy to romanticize; the data says trading every one you see is a path to losses.

Why it matters

Islands look like high-conviction signals — two gaps, an isolated chunk of price, a clean reversal. That visual drama is exactly why traders overweight them. Bulkowski's contribution is to show the numbers, which dethrone the pattern from its traditional reputation. The takeaway is twofold: (1) avoid islands entirely as a default, or (2) filter them aggressively for height, width, and context before trading.

The "nothing to reverse" failure mode

The single most common reason islands fail is that the trend they're "reversing" was barely a trend. An island top forming on top of a two-month sideways consolidation has nothing to reverse — once the second gap closes, price often resumes higher. Look for islands at the end of sustained, extended trends.

Gaps must be paired by price, not just sequence

Bulkowski's screening rule: the two gaps must overlap in price or sit within ~13 cents of each other, and each gap must be at least 25 cents tall. Otherwise the visual "island" is illusory — sequential gaps that happen to bracket some price action don't qualify if their price levels don't match.

Key takeaways

Mental model

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Practical application

A skeptic's island-trading checklist

Example

A biotech stock trades sideways between $45 and $50 for two months. It gaps up to $55 on a phase-2 trial readout. Over the next three weeks it trades in a tight $54-$57 range. Then it gaps down to $51 on competing trial results.

This looks like a classic island top — two clear gaps, isolated price action. But:

• The gaps don't quite overlap ($55 vs $51 — gap range of $4).
• Prior to the first gap, the stock was sideways, not in an uptrend. Nothing to reverse.
• Within three weeks, price is back to $55 and trades sideways again.

A textbook island failure. The pattern looked great visually, but the filters Bulkowski emphasizes — gap-overlap precision and extended prior trend — would have warned you off.

Contrast with a textbook win: a momentum stock rallies from $30 to $80 over four months. It gaps to $84, trades a two-week island at $83-$86, then gaps down to $84. Both gaps share the $84 price level. Prior trend is real. You short at $83 (next day after the second gap), stop above $86.50. Price slides to $68 over two months. That's the kind of setup that earns the trade.

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