当今天交易的最低价高于昨天的最高价或今天交易的最高价低于昨天的最低价，缺口即形成。
当后来的价格走势越过该缺口时，表明该缺口被回补。
有两条基本的原则：
1. 避免普通缺口；
2. 在缺口被交易量确认之后再交易（等量成交图突出了价格和交易量之间的关系）。
普通缺口
普通缺口出现在没有明显价格走势的市场中。缺口出现后不会出现新高或新低，并很快会被下面的价格走势回补。
下面事件导致的缺口应该被忽略：
• 价格根据应付红利调整时出现的除息缺口；
• 新股发行时的缺口；
• 期货合约到期日的缺口。
突破缺口
突破缺口通常伴随着高交易量，而且发生在价格突破交易区间之后。它们之后通常会出现新高或新低，回补的概率很小。
交易策略：上升趋势中的突破缺口，在突破后做多并在缺口的下方止损；下降趋势中出现突破缺口后做空并在缺口上方止损。
持续缺口
持续缺口出现在一段很强走势的中部位置，可以有效的预测趋势的幅度。它们也会伴随这新高或新低，这一点和衰竭缺口有所区别。持续缺口通常不会被回补。
交易策略：如果交易量很大（至少大于50%），交易方法类似于突破缺口。提前进场，等待新高或新低来确认价格走势。如果新高或新低没有出现，那么立刻平仓——它有可能是衰竭缺口。
衰竭缺口
衰竭缺口出现在一个很强走势的末端，是大趋势衰竭之后的最后一次涨，通常伴随着大的成交量。它们和持续缺口的区别是，衰竭缺口完成后价格不会出现新高或新低，并将很快被回补。
交易策略：上升趋势中出现衰竭缺口，做空或平掉多头头寸；下降趋势中的衰竭缺口，做多或者平掉空头头寸。
岛形反转
岛形反转是衰竭缺口出现之后，突破缺口在相反方向出现的一个很强的反转信号。它的交易策略和衰竭缺口一致。
Gaps
Gaps occur when the lowest price traded is above the high of the previous day or, conversely, when the highest price traded is below the previous day's low.
A gap is filled when the range of subsequent bars closes the gap.
There are two basic rules:
1. Avoid trading common gaps, and
2. Only trade gaps when they are confirmed by volume.
Equivolume charts highlight the interaction of price and volume.
Common Gaps
Common gaps occur in markets without a strong trend. They are not followed by new highs or new lows and are quickly closed in subsequent days' trading.
Some gaps are caused by events and should be ignored:
• Ex-dividend gaps occur as price adjusts on the day after a dividend becomes payable;
• New share issues; and
• Expiry of futures contracts.
Breakaway Gaps
Breakaway gaps are normally accompanied by heavy volume and occur when prices break out of a trading range. They are usually followed by a series of new highs in an upside breakout or, a series of new lows in a downside breakout, and are seldom closed.
Trading Rules
Upside Breakaway
If the gap is accompanied by heavy volume, go long and place a stop-loss at the lower end of the gap.
Downside Breakaway
If the gap is accompanied by heavy volume, go short and place a stop-loss at the upper end of the gap.
Continuation Gaps
Continuation gaps occur near the middle of strong trends and are useful in projecting how far the trend will continue. They are followed by new highs in an up-trend or new lows in a down-trend, which distinguishes them from exhaustion gaps. They are not normally closed.
Trading Rules
If volume is strong (up at least 50%), trade as for breakaway gaps. Enter the trade early and wait for new highs (or new lows in a down-trend) to confirm the pattern. If there are none in the next few days then exit immediately — it could be an exhaustion gap.
Exhaustion Gaps
Exhaustion gaps occur at the end of a strong trend and are the last surge before the trend expires, normally on heavy volume. They differ from continuation gaps in that they are not followed by new highs (in an up-trend) or new lows (in a down-trend) and are closed shortly afterwards.
Trading Rules
Upward Exhaustion Gap
Sell short (or close your long position) and protect yourself with a stop above the last high.
Downward Exhaustion Gap
Go long (or close your short position) with a stop below the latest low point.
Island Clusters
Look out for island clusters, identified by an exhaustion gap followed (after a few days) by a breakaway gap in the opposite direction, they are powerful reversal signals.
Trading Rules
Trade in the same way as exhaustion gaps.
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