道氏理論——趨勢
道瓊斯意識到價格曲線的高點和低點反轉時，就代表趨勢的改變。
牛市趨勢
牛市趨勢可以通過一輪又一輪的反彈來識別，反彈後每一輪都有新高，並且低點也比前一輪高。
牛市的開始：新高+更高的低點
牛市結束：高點和低點都比前一輪降低
熊市趨勢
每一次的反彈都沒有超越前一輪的高點，並且低點都低於前一輪的低點：不斷下降的高點和低點。
熊市通常開始於牛市之後：當反彈沒有突破上一輪的高點，並回落到上一輪的低點之下。熊市結束和牛市開始的形態特徵一致。當不斷下降的高點和低點被更高的高點打破之後怎麼辦？這是一個灰色區域，下面是對大規模調整的介紹。
大規模調整
牛市趨勢時的調整是當價格低點低於前一輪的低點，或者是熊市中高點高於上一輪高點。
一些純粹主義者認為，當新高和逐漸上升的低點這一規律被打破時，牛市就意味著結束。另外一些人認為，熊市只有一系列的不斷降低的高點和低點出現之後才能確認，同時也只有出現一系列升高的高點和低點出現才能確認牛市趨勢。
從實用性角度考慮，應當把價格調整視為原趨勢的改變。
• 當價格走出新高時，牛市確立。
• 價格低點低於上一輪低點時，牛市結束。
• 牛市結束後，熊市開始，反之亦然。
Dow Theory - Trends
Dow recognized that trends changed when the pattern of peaks and troughs reversed.
Bull Trends
A bull trend is identified by a series of rallies where each rally exceeds the highest point of the previous rally. The decline between rallies ends above the lowest point of the previous decline. A series of successive higher highs and higher lows.
The start of an up trend is signaled when price makes a higher low (trough), followed by a rally above the previous high(peak):
Start = higher Low + break above previous High.
The end is signaled by a lower high (peak), followed by a decline below the previous low (trough):
End = lower High + break below previous Low.
What if the series of higher Highs and higher Lows is first broken by a lower Low? There are two possible interpretations - see Large Corrections.
Bear Trends
Each successive rally fails to penetrate the high point of the previous rally. Each decline terminates at a lower point than the preceding decline. A series of successive lower highs and lower lows.
A bear trend starts at the end of a bull trend: when a rally ends with a lower peak and then retreats below the previous low. The end of a bear trend is identical to the start of a bull trend.
What if the series of lower Highs and lower Lows is first broken by a higher High? This is a gray area - see Large Corrections below.
Large Corrections
A large correction occurs when price falls below the previous low (during a bull trend) or where price rises above the previous high (in a bear trend).
Some purists argue that a trend ends if the sequence of higher highs and higher lows is broken. Others argue that a bear trend has not started until there is a lower High and Low nor has a bull trend started until there is ahigher Low and High.
For practical purposes, only accept large corrections as trend changes in the primary trend.
• A bull trend starts when price rallies above the previous high;
• A bull trend ends when price declines below the previous low;
• A bear trend starts at the end of a bull trend (and vice versa).
文章翻譯由兄弟財經提供
文章來源：http://www.incrediblecharts.com/technical/dow_theory_trends.php