“低买高卖”是一个著名的利用市场倾斜在上升和下降过程中赚取利润的格言。尽管它非常简单，但是却很难操作。在回顾时很容易看出特定点的高低，但是在当时，确是非常困难的。价格影响市场参与者的心理和情绪。
因为这个原因，“低买高卖”的持续执行是具有挑战性的。交易员可以使用工具，例如移动平均数和商业周期。
低买高卖中存在的困难
有著名的市场被驱动到极端的例子，市场泡沫中的高价和市场恐慌中的低价。这些被证明是低买高卖很好的机会。然而，已经发生了无数次市场持续在一个方向上的趋势，惩罚那些寻求低买高卖机会的人。在一天看起来是高点的价格在另一天看起来可能是低点。
交易员和投资者必须有一个特定客观方式判断价格是高还是低。人们习惯于随波逐流。持续低买高卖有固有的困难。当价格低时，对股票的情绪往往都是相当负面的。许多看涨持有人被迫抛售他们的股票。相同的，当价格低时，很难想象让一个赢家放手。
低买高卖在某种方式上被误导，因为低价和高价只用在回顾时才变得明显。总有看涨的人认为股票价格很低，看跌的人认为价格很高。通常，双方都提出令人信服的理由。对交易员和投资者的挑战是判断哪只股票由基本面驱动到了极端和哪只股票由情绪驱动。当价格由情绪驱动时均值回归策略更容易生效。
移动平均数
执行低买高卖策略的一个简单方式是使用移动平均数。移动平均数完全由价格得到的，而且他们在帮助交易员和投资者判断股票趋势时很有帮助。
使用一个较短时间的移动平均数和一个较长时间的移动平均数能够对交易员低买高卖有所帮助并能保护下行风险。例如，一个普遍的方式是使用50天和200天移动平均数。当50天移动平均数穿过200天移动平均数，则产生一个买入信号。当它穿过相反信号，则产生一个卖出信号。
这对交易员判断趋势即将结束时的入场点是十分有效的。低买高卖策略的一个问题是在趋势完全耗尽之前买入或者卖出。该方法避开了这个问题。
商业周期和情绪
一个低买高卖的方法，更适合使用商业周期和情绪调查作为市场时机工具的长期投资者。市场从恐慌到贪婪的长时间内遵循一个相对一致的模式。恐慌最大时是最好的买入时机，而贪婪则是最佳的高卖时机。
这些极端情况每十年都发生几次并有惊人的相似之处。这些情绪周期跟随商业周期。当经济衰退时，恐惧主导市场经济活动减少。这是低买的时机。
当经济周期在膨胀阶段，经济活动增加。通常，人们对未来乐观。这是高卖的时机。例如消费者信心调查的情绪调查为商业周期提供进一步的预见。
A Look At the Buy Low, Sell High Strategy
By Investopedia | August 14, 2015
"Buy low, sell high" is famous investing adage about taking advantage of the market's propensity to overshoot on the downside and upside. Although it is very simple, it is difficult to execute. It is easy to say whether a certain price is low or high in retrospect, but in the moment, it is monumentally difficult. Prices affect the psychology and emotions of market participants.
For this reason, "buy low, sell high" can be challenging to implement consistently. Traders can use tools, such as moving averages and the business cycle.
Difficulties in Buy Low, Sell High
There are famous examples of the market being driven to extremes, whether it is high prices during market bubbles or low prices during market panics. These proved to be excellent opportunities to buy low and sell high. However, there have been countless times when the market keeps trending in one direction, punishing those looking to buy low or sell high. What look like high prices one day may look like low prices another day.
Traders and investors must have a certain objective method to determine if prices are high or low. Humans are conditioned to follow the crowd. There is inherent difficulty in consistently buying low and selling high. When prices are low, sentiment tends to be overwhelmingly negative towards a stock. Many bullish holders are forced to dump their shares. Similarly, when price is high, it is difficult to conceive of letting go of a winner.
"Buy low, sell high" is misleading in some ways, as lows and highs only become clear in retrospect. There is always a bull who considers a stock price to be low and a bear who considers it high. Often, both sides make compelling arguments. The challenge for investors and traders is to determine which stocks are being driven to extremes by fundamentals and which are being driven by emotions. Mean-reversion strategies are more likely to work when price moves are driven by emotions.
Moving Averages
One simple way to implement a buy low, sell high strategy is with the use of moving averages. Moving averages are derived solely from price, and they are helpful in helping traders and investors determine a stock's trend.
Using a moving average of a shorter duration and one with a longer duration can assist in helping traders buy low and sell high as well as protect downside risk. For example, one common method is to use the 50-day and 200-day moving averages. When the 50-day moving average crosses the 200-day, it generates a buy signal. When it crosses the other way, it generates a sell signal.
This is effective in helping a trader time his entry to the point when the trend is faltering. One issue for buy low, sell high strategies is buying or selling before the trend has fully exhausted itself. This approach sidesteps the issue.
Business Cycle and Sentiment
An approach to buy high, sell low, more suited for long-term investors is to use the business cycle and sentiment surveys as market timing tools. The market follows a rather consistent pattern of moving from fear to greed over long periods of time. Times of maximum fear are the best time to buy stocks, while greed is the optimal time to sell high.
These extremes take place a couple times every decade and have remarkable similarities. These emotional cycles follow the business cycle. When the economy is in a recession, fear predominates as economic activity decreases. This is the time to buy low.
When the business cycle is in its expansion phase, economic activity is increasing. Typically, people are feeling optimistic about the future. This is the time to sell high. Sentiment surveys such as the Consumer Confidence Survey provide further insight into the business cycle.
本文翻译由兄弟财经提供
文章来源：http://www.investopedia.com/articles/investing/081415/look-buy-low-sell-high-strategy.asp