The challenge
挑战
For all their criticism of mainstream economists, the challenge for the behavioural school is to come up with a coherent model that can produce testable predictions about the overall economy. They have grown in influence with governments adopting their “nudge” ideas on how to influence behaviour; asking people to opt out of pension plans rather than opt into them, improves the take-up rate. In effect, the rules rely on inertia; people can't be bothered to fill in the forms required to opt out.
鉴于对主流经济学家的所有这些批评，行为经济学面临的挑战是提出一种能够就整体经济产生可验证的预测的一致模型。随着各国政府开始在如何影响行为这样的问题上采纳他们的一些“推动性”观点，行为经济学的影响力已经有所增长；要求人们退出养老金计划而不是加入养老金计划能够提高吸纳率。实际上，这些法规依靠的是惯性；谁愿意自找麻烦去填写退出养老金计划所需要的表格。
At the macro level, however, a coherent model is yet to emerge. George Cooper, a fund manager and author, has argued that economics needs the kind of scientific revolution driven by Newton and Einstein.
然而，在宏观层面，一致的模型至今还没有出现。基金经理兼作家George Cooper指出，经济学需要由牛顿和爱因斯坦所推动的那种科学革命。
The most promising approaches may be based on our growing understanding of the brain. Neuroscientists have shown that monetary gain stimulates the same reward circuitry as cocaine – in both cases, dopamine is released into the nucleus accumbens. “In the case of cocaine, we call this addiction. In the case of monetary gain, we call it capitalism' says Andrew Lo of the Massachsetts Institute of Technology.
最有前途的策略可能会以我们对大脑的日渐理解为基础。 神经科学家已经揭示出，钱财所得能够激起同可卡因一样的奖赏回路——在这两个例子中，多巴胺都被释放进入了伏隔核。“在可卡因的例子中，我们称之为上瘾；在钱财所得的例子中，我们称之为资本主义，”麻省理工的罗闻全如此说道。
Similarly the threat of financial loss apparently activates the same fight-or-flight response as a physical attack, releasing adrenalin and cortisol into the bloodstream. Risk-averse decisions are associated with the anterior insula, the part of the brain associated with disgust. In other words, we react to investment losses rather as we react to a bad smell.
同样，钱财损失的威胁也显然能够激活同物理攻击一样的战斗还是逃跑的反应，能够将肾上腺素和皮质醇释放到血液中。规避风险的决定与厌恶有关的那部分大脑——前脑岛有关系。换言之，我们对投资损失的反应恰如我们对某种坏气味的反应。
Another important finding is that humans would not improve their thinking if they turned into the emotionless Vulcans of Star Trek. Patients who have suffered damage to the parts of the brain most associated with emotional responses seem to have difficulty in making decisions. “Emotions are the basis for a reward-and-punishment system that facilitates the selection of advantageous behaviour” says Mr Lo. Humans also follow heuristics or “rules of thumb” that guide our responses to certain stimuli; these may have developed when mankind lived in much more dangerous surroundings. If you hear a rustle in the bushes, it may well not be a tiger; but the safest option is to run away first and assess the danger afterwards.
另一个重要的发现是，就算是人类变成《星际迷航》中的不感情用事的瓦肯人，他们也不会改进自己的思维。同情感反应关系最大的那部分大脑受过伤害的病人似乎在做决定方面存在着困难。“情感是利于有益行为选择的奖惩体制基础，”罗闻全说。人类还遵循指导我们对特定刺激做出反应的普遍规律；这些反应可能在人类生存环境比现在危险得多的时候就已经发展起来了。如果你听到灌木丛中有响动，很有可能不是一只老虎；但是最安全的选择就是先逃离，然后再评估危险。
In the second world war, bomber crews had the choice of wearing a parachute or a flak jacket; donning both was too bulky. The former helped if the plane was shot down, the latter protected crew from shrapnel caused by anti-aircraft fire. Getting hit by shrapnel was statistically more likely so the rational choice would be to wear the flak jacket every time. Instead the crews varied their garb, roughly in proportion to the chances of the two outcomes—although there was no way they could predict the outcome of a single mission.
在二战中，轰炸机驾驶员可以选择穿一件降落伞或是避弹衣；两件都穿会太臃肿。降落伞的用处在于飞机被击落时；避弹衣能够保护飞行员免遭防空炮火产生的弹片。从统计学来讲，被弹片击中的可能性更大。因此，理性的选择是每次都穿避弹衣。但是，飞行员每次穿的防护装备都不一样，大致同两种结果的可能性成正比——尽管他们无法预测每一次执行任务时的结果。
Mr Lo argues that this approach may sound arbitrary but such behaviour may be is rational from an evolutionary perspective. Take an animal that has a choice of nesting in a valley or a plateau; the valley offers shade from the sun (good for raising offspring) but vulnerability to floods (killing all offspring). The plateau offers protection from floods (good for offspring) but no shade (killing all offspring). The probability of sunshine is 75%. So the “rational” decision from the individual's perspective would be to stay in the valley. But if a flood occurs, the entire species would be wiped out. It makes more sense for the species if individuals probability match. “When reproductive risk is systematic, natural selection favours randomising behaviour to avoid extinction” he writes.
罗闻全指出，这种策略可能听上去是随意的；但是，从进化的角度来看，这样的行为可能是理性的。以既可以选择在山谷筑巢也可以选择在高坡筑巢的动物为例；山谷能够提供的背阴处（这有利于抚育幼崽），但是面对洪水，山谷是脆弱的（这会杀死所有的幼崽）；高坡能够提供免遭洪水的保护（这有利于养育幼崽），但是高坡没有背阴处（这会杀死所有的幼崽）。光照的可能性是75%。因此，从个体的角度来说，“理性的”决定是留在山谷中。但是，如果洪水爆发，整个物种都会被抹除。对于物种来说，如果个体的可能性满足这种情况，其意义就更加重大了。“当再生产的风险是系统性的情况下，自然选择倾向于随机行为以避免灭绝”他写道。
Mr Lo's view is that markets are normally efficient but not always and everywhere efficient. He dubs this “adaptive market theory”—and sees it as a consequence of human behaviour, particularly herd instinct. Watching other people suffer triggers an empathetic reaction. When other investors are panicking in a period of market turmoil, we tend to panic too.
罗闻全的观点是，市场一般是有效的，但并不是时时处处都有效。他称之为“选择性市场理论”——并视之为人类行为，尤其是从众本能的一个后果。看到别人受煎熬会激起一种同情的反应。当其他投资者在一段市场动荡期中惊慌失措时，我们往往也会惊慌失措。
A similar approach, dubbed the fractal market hypothesis, is advanced by Dhaval Joshi of BCA Research. This acknowledges that investors with different time horizons interpret the same information differently. “The momentum-based high frequency trader might interpret a sharp one-day sell-off as a sell signal” he says, “but the value-based pension fund might interpret the same information as a buying opportunity. This disagreement will create liquidity without requiring a big price adjustment. Thereby it also fosters market stability.”
一种被称之为分形市场假设的类似策略在BCA研究所的Dhaval Joshi那里得到了发展。这种策略认为，不同时区的投资者会对同一个信息作出不同的解读。“基于惯性走势的高频交易者可能会把某一天的抛售解读为卖出信号，”他说。“但是，基于价值投资的养老金基金可能会把同样的信息解读为买入机会。这种不一致会在不需要大的价格调整的情况下创造出流动性。因此，它还有利于市场的稳定。”
But if the different groups start to agree—groupthink, in other words—liquidity will evaporate as everyone wants to buy or sell at the same time. In such a situation, price changes may become violent. Mr Joshi thinks central bank interference in the markets is accordingly dangerous since it creates uniform mentality among investors in which easier monetary policy is always a good thing for asset prices.
但是，如果不同人群的观点开始趋向一致，也就是说形成一种群体性思维，随着在同一时间人人都想买入或者卖出，流动性将会蒸发殆尽。在这种情况下，价格的变动可能会变得非常剧烈。Joshi认为，相应地，央行之于市场的介入也是危险的，因为这种介入在投资者中制造出了宽松的货币政策总是利好于资产价格这样的统一心态。
Another area of research is to view the markets as a classic example of the principal-agent problem where many market participants are not investing their own money but acting on behalf of others. Paul Woolley and Dimitri Vayanos of the London School of Economics see this as a potential explanation for the momentum effect. Investors choose fund managers on the basis of their past performance; they will naturally pick those that have done well. When they switch, the successful manager will receive money that he will reinvest in his favourite stocks; by definition, these are likely to be stocks that have recently performed well. This inflow of cash will push such stocks up even further.
另一个研究领域是把市场视为委托代理问题——许多市场参与者不是在用自己的钱投资而是代表别人投资——的一个经典例子。伦敦政治经济学院的Paul Woolley和Dimitri Vayanos视之为惯性效应的一个潜在解释。投资者选择基金经理的基础是他们过去的业绩；因而，他们自然会选择已经做得很好的基金经理。当他们从一只基金转换到另一只基金时，成功的基金经理会收到他将再投资于自己所中意的股票的资金；根据定义，这些股票很可能是最近表现出色的股票。这种现金流入会推动这些股票进一步上涨。
Another example of the principal-agent mismatch at work may lie in the incentive structure for executives. Ironically, this all stems from an attempt to align the interests of executives and shareholders more closely. In the 1980s, academics worried that executives were too interested in empire-building—creating bigger companies that would justify bigger salaries for themselves—and not focusing on shareholder returns. So they were given options over shares. In the bull market of the 1980s and 1990s, these options made many executives extremely rich; CEO pay has risen eightfold in real terms since the 1970s. These riches have come at the price of impermanence; the average tenure of a CEO has fallen from 12 years to 6.
委托代理错配在起作用的另一个例子可能存在于针对企业高管的激励结构之中。具有讽刺意味的是，所有这些激励结构都是起源于将高管的利益与股东的利益更紧密地联系在一种尝试。上世纪80年代，学术界曾对高管将过多的兴趣放在打造商业帝国上面——创造出能够证明他们的高薪是正确的更大的公司——而不注重股东回报的行为感到忧心忡忡。因此，这些高管被给予了股票期权。在上世纪80年代和90年代的牛市中，这些期权曾让许多高管变得非常富有；自上世纪70年代以来，CEO的薪水已经上涨了8倍。这些富人的出现都是建立在不断变动的基础上的；CEO的平均任期已经从12年缩短至6年。
The combination may have made executives oversensitive to short-term fluctuations in the share price at the expense of long-term investment; a survey showed that executives would reject a project with a positive rate of return if it damaged the company's ability to meet the next quarter's earnings target. This may explain why record-low interest rates have not resulted in the splurge of business investment that economists and central bankers were hoping for. Again the financial system is not working well.
两者的结合可能已经让高管对股价的短期波动变得过于敏感，而这种敏感的代价就是长期投资。一份调查报告显示，高管会在一个正回报率的项目可能会对公司完成下一个季度的利润目标带来危害时拒绝这个项目。这可能解释了创记录的低利率为什么没能带来经济学家和央行所希望的商业投资大幅增加的原因。在此，又是金融体系没有很好地发挥其职能。
An evolving task
一个不断演进的任务
Another important issue for academics to consider is that the financial sector is not static. Each crisis induces changes in behaviour and new regulations that prompt market participants to adjust (and to find new ways to game the system). In any case, regulators cannot eliminate risk altogether. In terms of consumer protection, regulators cannot set a standard for the right product that should be sold in all circumstances. Investors' attitude towards risk may differ (indeed their ex ante willingness to take risk may differ from their ex post feelings when bad things happen.) And even if the salesman and the clients were equally well informed, the correct asset allocation (between, say, equities and bonds or America and Japan) cannot be known in advance.
值得学术界思考的另一个重要问题是，金融部门不是静止的。每一次危机都会带来行为方面的变化，以及能够促使市场参与者进行调整（并发现在体系中游戏的新方法）的新的监管措施。在任何情况下，监管者都不可能完全消除风险。就消费者保护而言，监管者不可能为可以任何情况下都被卖出的正确产品设定一个标准。投资者对于风险的态度可能是不一样的（实际上，他们在承担风险之前的意愿都有可能不同于他们在坏事发生后的事后意愿。）再者，即便是推销员和客户在获知消息方面是非常平等的，正确的资产配置（比如说，债券和股票或者是美国市场和日本市场的配置）也不可能事先获知。
Indeed, the attempt to create a riskless world may be counter-productive. Cliff Asness of AQR says that “Making people understand that there is a risk (and a separate issue, making them bear that risk) is far more important, and indeed far more possible than making a riskless world. And if I may go further, trying to create and worse, giving the impression you have created, a riskless world makes things much more dangerous.”
实际上，创造一个无风险的世界的尝试可能会到相反的作用。AQR的Cliff Asness说：“让人们理解风险的存在（并让他们去承担风险）要重要得多，而且其可能性实际上要比创造一个无风险的世界大得多。进一步说，创造并恶化一个无风险的世界的尝试，会让事情变得更加危险。”
There will never be an “answer” that eliminates all crises; that is not in the nature of finance and economics. But for too long economists ignored the role that debt and asset bubbles play in exacerbating economic booms and busts; it needs to be much more closely studied. Even if the market is efficient most of the time, we need to worry about the times when it is not. Academics and economists need to deal with the world as it is, not the world that is easily modelled.
永远也不会存在一种能够消除所有危机的“答案”；这不在金融和经济的属性之中。但是，经济学家忽视债务和资产泡沫在放大经济繁荣和加重经济泡沫中所扮演的角色已经太长时间了；经济的繁荣和泡沫需要得到更加密切的研究。即便市场在大多数时间中都是有效的，我们也需要为无效的时刻而担忧。学者和经济学家需要同现实的世界打交道，而不是同那个很容易被模型化的世界打交道。
