Cathy Pareto 2016年8月13日
当涉及钱和投资，我们不总是像我们想的那么理性，这就是为什么有一个整体的领域来研究我们时常的奇怪行为。你适合做一个投资者吗？行为金融学的理论和研究可能帮助你回答这一问题。
行为金融学：理性假设的质疑
许多经济理论都基于这样一个理念，即个人行为是以理性的方式进行的并且所有现存信息都是嵌入到投资过程里的。这一理念是市场假说有效性的关键。
但是质疑这一假说的研究人员发现有证据表明理性行为并不向我们认为那样的普遍存在。行为金融学试图理解和解释在决定形成过程中人类感情是怎样影响投资者的。你会对他们的发现感到震惊。
事实
2001年，金融服务研究公司Dalbar发布了一篇名为“投资者行为量化分析”的研究报告，其结论是普通投资者不能获得市场指数的回报。报告发现在截止到2000年12月的17年时间里，标准普尔的年均回报率为16.29%，而传统股票投资者的年均回报率在这期间仅为5.32%，差异惊人的达到9%。
研究还发现，在同一时期，固定收益投资者的年均收益仅为6.08%，而同期的长期政府债务指数收益则高达11.83%。
在2015年发表的相同报告中，Dalbar再次总结到普通投资者不能获得市场指数等额的回报。研究发现普通证券投资基金投资者获得的回报比标准普尔500低8.19%。更广泛市场回报是普通股票投资基金投资者获得回报的两倍多。
普通固定收益共同基金投资获得的回报也比债券市场低4.81%。
为什么会发生这样的现象呢？可能会有无数个解释。
后悔理论
后悔理论解释人们意识到判断错误后的情绪反应。面对抛售一种持有股票的前景时，投资者的情绪将会受到他们购买股票时价格的影响。
因此，他们把拒绝出售该股票作为避免后悔做出糟糕投资和面对尴尬亏损报告的方式。我们都会犯错，不是吗？
在考虑出售一支股票时投资者真正应该问自己的是：“如果这支股票已经清算，我重新购买会出现什么结果呢，我是否应该对其进行再次投资？”
如果答案是否定的，那么出售的时间已经到了。另外，这个结果是后悔购买一支亏损股票并且后悔没有在事实清晰的表明这个投资是错误时没有出售，这是一个恶性循环，避免后悔导致了更多的后悔。
后悔理论还适用于投资者发现他们曾经打算购买的股票价格上涨时。一些投资者为了避免这种后悔出现根据大众观点购买股票而且只购买那些旁人也购买的股票，用“大家都在这么做”来解释他们的决定。
奇怪的是，许多人在大多数人都持有的流行股票上亏损时的尴尬要比在那么不知名和不受欢迎股票上亏损时小的多。
心理价格
人类倾向于把特殊事件在心里计算价格，这些心理价格的有时候对我们行为的影响会比事件本身大得多。
举例来说，你想去当地剧院看演出，门票是20块。当你到了之后突然发现你丢了20快，那么你还会去买票吗？
行为金融学发现在这种情况下88%的会去买票。现在让我们假设你提前花20块买了票。当你到门口的时候发现你的票落家了。你会再花20块另买一张票吗？
只有40%的受调查对象会另买一张。然而，在两种情况下你都会支出40块。情况不同，钱的数量相同，心理价格不一样。这是不是很蠢？
能最好诠释心理价格的投资案例是犹豫出售一种曾经达到巨大收益但是现在收益却一般的投资。在经济繁荣和牛市市场中，人们习惯于健康的字面收益。当市场修正使投资的净值降低，他们会犹豫是否以降低的利润出售。他们会形成曾经获得巨大收益的心理价格，导致等待回到那个收益水平的价格。
前景理论/损失厌恶理论
不用咨询心理医生我们也知道相对于不确定回报人们更喜欢确定投资回报，我们在承担额外风险时想要获得回报。这是很合理的。
这里有一点很奇怪。前景理论认为人们对收益和亏损的感情程度不一样。人们在面对亏损前景时的紧张程度比等值的收益前景时的高兴程度大。
当报告客户的投资组合获得50万收益时，投资顾问的电话不一定会响个不停。但是我们可以确定如果是亏损50万，他的电话一定会被打爆。等值的亏损获得的关注程度永远比收益大，钱进入你的口袋后价值就会发生变化。
前景理论也解释了为什么投资者继续持有亏损的股票，因为相对于现实的收益，人们更乐意承受更多的风险。因为这个原因，投资者宁愿呆在股票的高风险位置，期待价格反弹。接连失败的赌徒会出现类似的行为，他们会加倍下注以希望收回原来的亏损。
因此，尽管我们希望对承担的风险获得理性回报，我们通常会倾向于把我们持有某些东西的价格看得高于我们原来想要出售的价格。
厌恶亏损理论指出了投资者出售盈利股票继续持有亏损股票的另一个原因，他们相信现在亏损的股票将来的表现可能好于现在盈利的股票。调查表名，流入表现良好共同基金的资金要比流出表现不佳的对冲基金的资金要频繁的多。
锚定
由于缺乏更好或者新的信息，投资者通常假设市场价格是正确价格。人们更倾向于相信最近的市场观点、看法和事件，并且错误推断区别于历史、长期平均值和概率的最近趋势。
在牛市中，投资者决定通常会受到价格锚的影响，这些价格锚是是被视为意义重大的价格，原因是他们是最近价格。这使得过去的决定回报和投资者决定不相关。
过度/过低反应
当市场上升时投资变得乐观，会假设这一趋势会持续。相反，投资者在市场下跌期间会变得非常悲观。这是锚定或者过分重视最近事件而忽视历史数据的结果，这是一种过度反应，使导致市场事件的坏消息出现时价格下跌太多而好消息则上涨太多。
在乐观的高峰期，投资者涌向那些超过其内在价值的股票。什么时候开始投资零收益和无限市盈率的股票的决定变得合理了呢？
对市场事件过度/过低反应可能会导致市场恐慌和崩溃。
过分自信
人们通常认为自己的能力高于平均水平。他们通常高估他们的知识和其他关于知识的能力。
许多投资者认为他们可以不断的进行波段操作，然而事实上有大量的证据表明他们是错误的。过分自信导致过多交易，交易成本使利润降低。
反面意见：非理性行为是异常现象吗？
正如我们之前提到的，行为金融学理论与传统金融观点直接冲突。他们都试图解释投资者行为和这些行为的暗示。那么谁是正确的呢？
和行为金融学冲突最激烈的是Eugene Fama和Ken French提出的有效市场假说（EMH）。他们的理论认为市场价格能否有效包含所有现有信息取决于投资者是否理性。
EMH的支持者认为行为金融学只能解释短期异常事件或者几率性结果，而在长期中这些异常将消失并回归到市场有效性假说中。
因此，可能没有充足的证据表明市场有效性假说应该被抛弃，因为过去的经验表明市场会在长期过程中纠正自己。在其《以上帝为对手: 风险传奇(概率与经济)》一书中，Peter Bernstein对辩论中利害攸关的问题做了很好的阐述：“重要的是了解市场不按传统经典模式设想的行事，有许多证据表明，行为金融学关于投资者非理性的观点与事实一致，但是我不知道你能怎样利用这些信息管理资金。我仍然不相信有人能不利用它一直赚钱。”
总结
行为金融学当然反映了一些嵌入投资系统的观点。行为主义者会说投资者通常会进行不理性行为产生无效市场和对股票错误定价，更不用说获得赚钱机会。
这在一时可能是正确的，但是不断揭露这些无效性是非常困难的。问题仍然在于这些行为金融学理论是否能被用来有效的管理你的资金。
也就是说，投资者是他们自己最大的敌人。试图看透市场在长期中不会产生回报。事实上，这通常会导致奇怪的非理性行为，从而引起你的资产贬值。
实行一个深思熟虑的策略并且坚持下去可以帮助你避免这些常见的错误。
Understanding Investor Behavior
By Cathy Pareto | Updated August 13, 2016 — 6:08 AM EDT
When it comes to money and investing, we're not always as rational as we think we are - which is why there's a whole field of study that explains our sometimes-strange behavior. Where do you, as an investor, fit in? Insight into the theory and findings of behavioral finance may help you answer this question.
Behavioral Finance: Questioning the Rationality Assumption
Much economic theory is based on the belief that individuals behave in a rational manner and that all existing information is embedded in the investment process. This assumption is the crux of the efficient market hypothesis.
But researchers questioning this assumption have uncovered evidence that rational behavior is not always as prevalent as we might believe. Behavioral finance attempts to understand and explain how human emotions influence investors in their decision-making process. You'll be surprised at what they have found.
The Facts
In 2001 Dalbar, a financial-services research firm, released a study entitled "Quantitative Analysis of Investor Behavior", which concluded that average investors fail to achieve market-index returns. It found that in the 17-year period to December 2000, the S&P 500 returned an average of 16.29% per year, while the typical equity investor achieved only 5.32% for the same period - a startling 9% difference!
It also found that during the same period, the average fixed-income investor earned only a 6.08% return per year, while the long-term Government Bond Index reaped 11.83%.
In its 2015 version of the same publication, Dalbar again concluded that average investors fail to achieve market-index returns. It found that "the average equity mutual fund investor underperformed the S&P 500 by a wide margin of 8.19%. The broader market return was more than double the average equity mutual fund investor’s return. (13.69% vs. 5.50%)."
Average fixed income mutual funds investors also under performed at a 4.18% under the bond market.
Why does this happen? There are a myriad of possible explanations.
Regret Theory
Fear of regret, or simply regret, theory deals with the emotional reaction people experience after realizing they've made an error in judgment. Faced with the prospect of selling a stock, investors become emotionally affected by the price at which they purchased the stock.
So, they avoid selling it as a way to avoid the regret of having made a bad investment, as well as the embarrassment of reporting a loss. We all hate to be wrong, don't we?
What investors should really ask themselves when contemplating selling a stock is, "What are the consequences of repeating the same purchase if this security were already liquidated and would I invest in it again?"
If the answer is "no", it's time to sell; otherwise, the result is regret of buying a losing stock and the regret of not selling when it became clear that a poor investment decision was made - and a vicious cycle ensues where avoiding regret leads to more regret.
Regret theory can also hold true for investors when they discover that a stock they had only considered buying has increased in value. Some investors avoid the possibility of feeling this regret by following the conventional wisdom and buying only stocks that everyone else is buying, rationalizing their decision with "everyone else is doing it".
Oddly enough, many people feel much less embarrassed about losing money on a popular stock that half the world owns than about losing on an unknown or unpopular stock.
Mental Accounting
Humans have a tendency to place particular events into mental compartments, and the difference between these compartments sometimes impacts our behavior more than the events themselves.
Say, for example, you aim to catch a show at the local theater and tickets are $20 each. When you get there you realize you've lost a $20 bill. Do you buy a $20 ticket for the show anyway?
Behavior finance has found that roughly 88% of people in this situation would do so. Now, let's say you paid for the $20 ticket in advance. When you arrive at the door, you realize your ticket is at home. Would you pay $20 to purchase another?
Only 40% of respondents would buy another. Notice, however, that in both scenarios you're out $40: different scenarios, same amount of money, different mental compartments. Pretty silly, huh?
An investing example of mental accounting is best illustrated by the hesitation to sell an investment that once had monstrous gains and now has a modest gain. During an economic boom and bull market, people get accustomed to healthy, albeit paper, gains. When the market correction deflates investor's net worth, they're more hesitant to sell at the smaller profit margin. They create mental compartments for the gains they once had, causing them to wait for the return of that gainful period.
Prospect/Loss-Aversion Theory
It doesn't take a neurosurgeon to know that people prefer a sure investment return to an uncertain one - we want to get paid for taking on any extra risk. That's pretty reasonable.
Here's the strange part. Prospect theory suggests people express a different degree of emotion towards gains than towards losses. Individuals are more stressed by prospective losses than they are happy from equal gains.
An investment advisor won't necessarily get flooded with calls from her client when she's reported, say, a $500,000 gain in the client's portfolio. But, you can bet that phone will ring when it posts a $500,000 loss! A loss always appears larger than a gain of equal size - when it goes deep into our pockets, the value of money changes.
Prospect theory also explains why investors hold onto losing stocks: people often take more risks to avoid losses than to realize gains. For this reason, investors willingly remain in a risky stock position, hoping the price will bounce back. Gamblers on a losing streak will behave in a similar fashion, doubling up bets in a bid to recoup what's already been lost.
So, despite our rational desire to get a return for the risks we take, we tend to value something we own higher than the price we'd normally be prepared to pay for it.
The loss-aversion theory points to another reason why investors might choose to hold their losers and sell their winners: they may believe that today's losers may soon outperform today's winners. Investors often make the mistake of chasing market action by investing in stocks or funds which garner the most attention. Research shows that money flows into high-performance mutual funds more rapidly than money flows out from funds that are underperforming.
Anchoring
In the absence of better or new information, investors often assume that the market price is the correct price. People tend to place too much credence in recent market views, opinions and events, and mistakenly extrapolate recent trends that differ from historical, long-term averages and probabilities.
In bull markets, investment decisions are often influenced by price anchors, which are prices deemed significant because of their closeness to recent prices. This makes the more distant returns of the past irrelevant in investors' decisions.
Over-/Under-Reacting
Investors get optimistic when the market goes up, assuming it will continue to do so. Conversely, investors become extremely pessimistic during downturns. A consequence of anchoring, or placing too much importance on recent events while ignoring historical data, is an over- or under-reaction to market events which results in prices falling too much on bad news and rising too much on good news.
At the peak of optimism, investor greed moves stocks beyond their intrinsic values. When did it become a rational decision to invest in stock with zero earnings and thus an infinite price-to-earnings ratio (think dotcom era, circa year 2000)?
Extreme cases of over- or under-reaction to market events may lead to market panics and crashes.
Overconfidence
People generally rate themselves as being above average in their abilities. They also overestimate the precision of their knowledge and their knowledge relative to others.
Many investors believe they can consistently time the market, but in reality there's an overwhelming amount of evidence that proves otherwise. Overconfidence results in excess trades, with trading costs denting profits.
Counterviews: Is Irrational Behavior an Anomaly?
As we mentioned earlier, behavioral finance theories directly conflict with traditional finance academics. Each camp attempts to explain the behavior of investors and implications of that behavior. So, who's right?
The theory that most overtly opposes behavioral finance is the efficient market hypothesis (EMH), associated with Eugene Fama (Univ. Chicago) & Ken French (MIT). Their theory that market prices efficiently incorporate all available information depends on the premise that investors are rational.
EMH proponents argue that events like those dealt with in behavioral finance are just short-term anomalies, or chance results, and that over the long term these anomalies disappear with a return to market efficiency.
Thus, there may not be enough evidence to suggest that market efficiency should be abandoned since empirical evidence shows that markets tend to correct themselves over the long term. In his book "Against the Gods: The Remarkable Story of Risk" (1996), Peter Bernstein makes a good point about what's at stake in the debate:
"While it is important to understand that the market doesn't work the way classical models think - there is a lot of evidence of herding, the behavioral finance concept of investors irrationally following the same course of action - but I don't know what you can do with that information to manage money. I remain unconvinced anyone is consistently making money out of it."
Conclusion
Behavioral finance certainly reflects some of the attitudes embedded in the investment system. Behaviorists will argue that investors often behave irrationally, producing inefficient markets and mispriced securities - not to mention opportunities to make money.
That may be true for an instant, but consistently uncovering these inefficiencies is a challenge. Questions remain over whether these behavioral finance theories can be used to manage your money effectively and economically.
That said, investors can be their own worst enemies. Trying to out-guess the market doesn't pay off over the long term. In fact, it often results in quirky, irrational behavior, not to mention a dent in your wealth.
Implementing a strategy that is well thought out and sticking to it may help you avoid many of these common investing mistakes.
本文翻译由兄弟财经提供
文章来源：http://www.investopedia.com/articles/05/032905.asp?rp=i