Key Reversal Day Complete Guide

What is Key Reversal Day?

A Key Reversal Day is a potent one-bar price pattern that signals a potential change in the prevailing trend. It is characterized by extreme price action where the market makes a new high (in an uptrend) or a new low (in a downtrend) but fails to sustain that momentum, ultimately closing beyond the previous day's closing price in the opposite direction. In a bearish key reversal, the price opens higher, hits a new high for the move, but then collapses to close below the previous day's close. Conversely, a bullish key reversal sees a new low followed by a close above the previous day's close. Technically, this pattern represents a 'blow-off' or an exhaustion of the current trend. According to Thomas Bulkowski’s research on outside days (a closely related formation), the performance of these patterns as standalone signals can be mixed, often acting more as short-term trend interruptions than major trend changes unless accompanied by significant volume. Bulkowski notes that for bearish outside days in a bull market, the price continues to drop only about 52% of the time, which is close to a random walk. However, when the reversal occurs on high volume—typically at least 50% above the 10-day average—the reliability increases substantially. Steve Nison’s work on candlesticks parallels this with the 'Engulfing' pattern, emphasizing that the broader the range of the reversal bar relative to the preceding bar, the more significant the signal. The psychological shift is key: the initial move to a new extreme traps late-entering trend followers, while the subsequent reversal triggers stop-loss orders, fueling the move in the new direction. Analysts look for this pattern at established support or resistance levels to confirm its validity.

Identification Rules

1. 相場のトレンドに対して、弱気の場合は直近高値を、強気の場合は直近安値を更新する必要がある。
2. The closing price must be below the previous day's close for a bearish reversal, or above it for a bullish reversal.
3. 日中の価格変動幅（高値から安値）は、通常、前日の変動幅を超え、しばしばそれを包み込む。
4. The pattern is most valid when it occurs after a prolonged trend and is accompanied by a surge in volume.

References

• Thomas N. Bulkowski (2005). Encyclopedia of Chart Patterns.
• Steve Nison (2001). Japanese Candlestick Charting Techniques.

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