出自Investopedia 2015年11月13日
“羊群效應”在投資字典裡指投資者盲目跟從已經建立的投資趨勢或者模式。這些交易員是投資公理“趨勢是你的朋友”的典型信徒。因為一些原因這一原則在外匯交易會比在股票交易中提供更好的回報。
首先，外匯交易受技術分析的影響比股票交易大，而基本面分析在股票中影響要比外匯大。其次，雖然外匯市場是全球最具流動性的金融市場，在2000年日交易量達到4萬億美元，但是其中6個貨幣（美元/歐元、美元/日元、美元/英鎊、美元/澳元、美元/瑞郎 和 美元/加元）的交易量卻占總量的三分之二。
這些貨幣時刻被世界各地的外匯交易員密切關註，同時有大量的監控設備日夜不停的監視以尋找買進和賣出的機會。一旦出現關鍵技術信號，交易員立刻加入並增強原來趨勢，從而加劇羊群效應。
在外匯交易中運用羊群效應
在外匯交易中使用羊群效應的指導原則非常簡單，那就是根據大多數人的觀點和已經建立的全球市場趨勢進行交易。如果你足夠精明，在股票市場進行反向交易可能使你收益頗豐，但是這在外匯市場將是個災難的開始，外匯可以無視基本面的時間超出你的想象。
2013年的日元下跌是羊群效應的很好案例。在4月，日本央行宣佈將買進政府債券並在2014年加倍貨幣基數。日本央行企圖以這個前所未有的貨幣政策刺激經濟增長和打破日本長達20年的通縮怪圈。
交易員在2013年因為日本人口老齡化和巨額政府債務開始做空日元，由於交易員相信日本央行將繼續實行寬松貨幣政策，日元下跌加劇。在2013年5月的第一個週，日元成為當時下跌幅度最大的貨幣，相對美元下跌12.4%。隨著交易員蜂擁湧向做空日元，羊群效應增加了日元下跌的勢頭。
在2013年底，做空日元/美元實際上取代了做空歐元/美元，趨勢交易員的註意力從歐元反彈到1.20後集中到了日元上。該轉變可以在到2013年5月7日的一年中與美元對比看出來，歐元上升了0.32%，而日元下跌了19.3%。
羊群效應也在2013年美元對大多數貨幣變強中表現出來，美元在那時對16個主要貨幣中的13個增值。那時的美元變強很大程度上歸功與美國經濟回暖，使道瓊斯工業平均指數和標準普爾500指數達到歷史最高點，進一步吸引資本流入進入一個良性循環。
普通羊群效應外匯交易
過去幾年的貨幣行為表明以下交易是主要的普通羊群效應。這只是建議，如果你想交易這些貨幣，強烈建議您做好自己的調查。
中國是許多大宗商品的最大進口國，當中國經濟強勁，大宗商品出口國的貨幣將會受益，例如加元和澳元。在本世紀前10年中，由於中國經濟的飛速增長對大宗商品的需求大幅增加，澳元和加元相對美元增值了37%。因此，在中國經濟形勢良好時可以考慮做多加元/美元和澳元/美元。
加元和澳元在全球經濟增長強勁和對風險偏好的需求強烈時表現良好。相反，當出現擔憂全球經濟放緩和風險偏好縮減，這些大宗商品貨幣下跌並且例如美元和瑞郎這樣的避險貨幣開始上升。在這時，主流的羊群效應是做空加元或者澳元，做多美元或者瑞郎。
雖然日元在2013年春天日元損失了大量價值，但是因為其“套利交易”的流行使其交易與全球風險偏好相反。當風險偏好消失和驚慌的投資者蜂擁交易時可能是個災難，因為對風險資產的減價出售和因償還貸款而對日元巨大需求引起的匯率上升將成為雙重巨大打擊。在2007年對日元的套利交易超過1萬億美元，但是2008年全球經濟崩潰，日元對美元上升了20%。
羊群效應技巧
無經驗的外匯交易員應該註意這些羊群效應技巧：
警惕一個陳腐或長期存在的趨勢，因為它隨時會發生反轉的風險。貨幣趨勢可以逆轉非常強烈，錯誤的方向可能引起災難性損失。就像一些人說的，除非你是喬治索羅斯，否則不要進行貨幣反向交易。
當在一個趨勢中交易時，提前制定推出策略。從衆可以提供安全性，只要你在大家退出時不被落下。
止損至關重要，因為高槓桿的外匯交易在交易策略沒有嚴格執行時會引發大量經濟損失。
不要忘了你在做多一種貨幣時正在做空另一種。做空更容易關註，這種方法可以避免自滿而使盈利變成虧損。
不建議對虧損倉位進行補倉，降低平均持有價格在外匯交易中是個不怎麼可行的策略。
總結
羊群效應可以幫助你在已經建立的趨勢中獲利，但是要使用止損、避免自滿和制定退出策略。無數的交易以巨大的代價證明，趨勢是你的朋友，但是它會有終止的時候。
Herd Instinct Often A Good Guide For Forex
By Investopedia Staff | Updated November 13, 2015
"Herd instinct" in the investing lexicon refers to the tendency of traders to blindly follow an established investment trend or pattern. Such traders are typically adherents of the well-known investment axiom "the trend is your friend." This principle is likely to provide better returns in forex trading than in equities trading for a couple of reasons.
Firstly, forex trading is arguably driven by technical analysis to a greater extent than stock trading, given that fundamental analysis plays a much bigger part in the latter than it does in the former. Secondly, while the forex market is the world's most liquid financial market with estimated daily turnover exceeding $4 trillion in 2010, just six currency pairs – USD/euro, USD/yen, USD/sterling, USD/Australian dollar, USD/Swiss franc and USD/Canadian dollar – accounted for two thirds of this trading volume. (Conversely, blue-chip stocks on the major global equity exchanges collectively number in the thousands).
These currencies are avidly watched by legions of currency traders around the world, and the same technical levels are monitored around-the-clock by these traders for buy and sell signals. Once a key technical gives way, other traders jump in and reinforce the initial trend, thus exacerbating the herd effect.
Using Herd Instinct in Forex
The guiding principle for using the herd instinct profitably in the forex market is a simple one – base your trades on the majority view and established trends in global markets. Being a contrarian may enable you to reap rewards in the stock market – assuming that you are astute enough to time the markets effectively – but it can be a recipe for disaster in the forex market, where a currency can defy fundamentals for so long and drift so far that it can test the resolve of the biggest and best traders.
The decline of the Japanese yen in 2013 is a prime example of the herd instinct at work. In April 2013, the Bank of Japan (BOJ) announced that it would buy government bonds and double the country's monetary base by 2014. The BOJ embarked on this unprecedented degree of monetary stimulus to foster growth and break the deflationary spiral that had plagued the Japanese economy for two decades. As a result, the short JPY/long USD trade was one of the most popular forex trades in the first half of 2013.
While traders were already shorting the yen going into 2013 on account of Japan's aging population and massive government debt, the yen's descent picked up steam as traders and speculators grew increasingly confident that the Bank of Japan would continue to ease monetary policy. By the first week of May 2013, the yen was the biggest decliner of the major currencies for the year, with a 12.4% fall versus the U.S. dollar. With forex traders rushing to put on short JPY positions, the currency looked set to break the 100 barrier, at which point the herd instinct would have added to its downward momentum.
The short JPY/long USD trade had in fact superseded the short EUR/long USD trade by 2013 as the "go to" trade for trend followers, as the attention of currency bears shifted to the Japanese currency following the euro's rebound since mid-2012 from a low of around 1.20. This sentiment shift could be gauged by the performance of the two currencies versus the greenback in the one-year period ending May 7, 2013; while the euro had gained 0.2%, the yen was down 19.3%.
The herd instinct was also evident in the strength of the U.S. dollar against most major currencies by May 2013, with the greenback on the ascent against 13 of the 16 most widely-traded currencies. The unexpected strength of the U.S. dollar at that time was largely attributed to the rebounding U.S. economy, which had driven the Dow Jones Industrial Average and S&P 500 indexes to record highs, attracting further capital inflows in a virtuous circle.
Common Herd Instinct Forex Trades
Currency action over the years indicates that the following trades are the most common "herd instinct" ones. These are only suggestions, and if you intend to trade these currencies, it is strongly recommended that you conduct your own research and due diligence.
As China is the world's biggest importer of numerous commodities, when the Chinese economy is growing strongly, currencies of commodity exporters such as Canada and Australia benefit. In the first decade of this millennium, as commodity demand soared due to the Chinese boom, the AUD and CAD surged 37% against the U.S. dollar. Therefore, consider going long CAD and AUD versus the greenback when the Chinese economy is expanding rapidly.
The AUD and CAD tend to do well when the global economy is growing strongly and demand for risk appetite is strong. Conversely, when fears abound about slow global growth and risk appetite shrinks, these commodity currencies decline and safe-haven currencies such as USD and Swiss franc (CHF) rise. At such times, popular herd instinct trades are short CAD or AUD and long USD or CHF.
While the Japanese yen had lost substantial ground by spring of 2013, it has tended to trade in a direction opposite to that of global risk appetite because of its popularity as a funding currency for "carry trades*." The carry trade strategy can be disastrous when risk appetite vanishes and panicked speculators rush to close their positions, because of the double whammy arising from the fire-sale of risky assets and the spike in the yen exchange rate due to demand for the currency to repay carry loans. More than $1 trillion had been invested in the yen carry trade by 2007, but as the global economy unraveled in 2008, the currency rose 20% versus the greenback that year.
Herd Instinct Tips
Inexperienced forex traders should note these "herd instinct" tips:
Beware of a stale trend or a long-lived one, since it may be in danger of imminent reversal. Currency trends can reverse quite sharply, and being on the wrong end of a trend reversal can lead to catastrophic losses. By the same token, unless you're George Soros, don't be a currency contrarian.
While playing a trend, plot your exit strategy in advance. Staying in a herd can provide safety in numbers, as long as you don't get crushed when the herd stampedes for the exits.
Stop losses are very critical, since the inordinately high degree of leverage in retail forex can lead to financial ruin if strict trading discipline is not implemented.
Don't forget that being long one currency means you are short the other. Short positions seem to warrant closer monitoring by traders, and this approach may help avoid the complacency that can turn a profitable position into a losing one.
Adding to a losing position is not advisable, since "averaging down" is seldom a viable trading strategy in forex.
The Bottom Line
The herd instinct can help you profitably trade established trends in forex; but use caution and commonsense within the herd – use stop losses, avoid complacency and plan your exit strategy. As innumerable traders have discovered to their cost, the trend is your friend, but only until it comes to an end.
本文翻譯由兄弟財經提供
文章來源：http://www.investopedia.com/articles/forex/050913/trade-forex-herd-instinct.asp