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Finance & economics
財經版塊
Buttonwood
梧桐樹專欄
Risk off
風險消失
Why financial markets are so oddly calm.
為什么金融市場如此詭異地平靜。
One thing nobody thinks of Donald Trump’s return to the White House is that it will herald four years of quiet, predictable government.
沒有人認為唐納德·特朗普重返白宮預示著四年平靜、可預測的政府。
Here, then, is a puzzle for readers interested in the more abstract bits of finance.
如果有讀者對金融中比較抽象的部分感興趣，那么這里有一個給這些讀者的謎題。
Why was Mr Trump’s re-election greeted by resounding drops in volatility all across the world’s most important markets?
為什么特朗普再次當選會在全球最重要的幾個市場上引起波動率大幅下降？
First, a primer for those who slept through Quantitative Finance 101.
首先，為那些在“量化金融導論課”上睡過去的人介紹一些入門知識。
Volatility is commonly used as a proxy for uncertainty or risk, and describes how much asset prices fluctuate.
波動率通常被用于指代不確定性或風險，描述了資產價格波動的程度。
Historical volatility measures the spread of past daily price movements, telling you how far you should expect any given value to be from the average.
歷史波動率衡量過去每日價格變動的差額，告訴你任何給定價值與平均值的預期偏差程度。
Say, for instance, you are told that a stockmarket index has had an average annual return of 10%, with a volatility of 20%.
比如說，有人告訴你，一個股票市場指數的平均年回報率為10%，波動率為20%。
That means that in roughly two-thirds of previous years, the index’s returns were somewhere between -10% and 30%.
那么這意味著在過去大約三分之二的年份里，該指數的回報率在-10%至30%之間。
Higher volatility would have meant more turbulent markets and a wider range.
較高的波動率意味著市場更加動蕩，波動幅度更大。
Lower volatility would have meant a tighter range and more millpond-like markets.
較低的波動率意味著波動幅度更小，市場更風平浪靜。
So much for the rear-view mirror—investors care more about what lies ahead.
后視鏡里的東西就這么多，投資者更關心前方的情況。（已知的理論東西就這些，投資者關心未來會發生什么。）
This, of course, is harder to determine.
當然，未來的情況是更難確定的。
But if the market expects big swings in prices, traders will seek more insurance against such swings than they would if they expected conditions to be placid.
但如果市場預計價格會大幅波動，那么交易員會比預計市場狀況平靜時尋求更多的保險措施來抵御這種波動。
These expectations, therefore, dictate the cost of insurance contracts, or “options”.
因此這些預期決定了保險合同或者說“期權”的價格。
Apply some maths worked out in the 1970s by Fischer Black and Myron Scholes, two economists, and you can work backwards, converting options prices into “implied volatility”.
運用兩位經濟學家費希爾·布萊克和邁倫·斯科爾斯在20世紀70年代提出的一些數學方法，你就可以反向推導，將期權價格轉換為“隱含波動率”。
You now have the market’s collective judgment on how jumpy asset prices will be.
現在你就有了市場對資產價格波動程度的集體判斷。
The surprise is that, as traders rushed to price in Mr Trump’s sweeping victory, the collective judgment reached in the biggest markets of all was: “a lot less jumpy than before”.
令人驚訝的是，當交易員們匆忙把特朗普的全勝算入市場時，所有最大市場達成的集體判斷是“比以前穩定多了”。
Election day set off a plunge in the VIX index, which measures the implied volatility of the S&P 500 share index of large American firms.
選舉日引發了VIX指數（注：芝加哥期權交易所波動率指數）的暴跌，該指數衡量的是美國大型公司的標準普爾500股票指數的隱含波動率。
The MOVE index, the equivalent for dollar interest rates, followed suit.
MOVE指數（注：衡量美國國債波動性的指數）相當于美元利率，也隨之暴跌。
So did the volatility of the exchange rate between dollars and euros, the world’s most heavily traded currency pair, and of that between dollars and yen, the second-most-traded pair.
美元與歐元之間的匯率波動率也暴跌，這兩種貨幣是世界上交易最頻繁的貨幣對，美元和日元的匯率波動率同樣暴跌，這兩者是交易第二頻繁的貨幣對。
Share prices soaring on the promise of tax cuts are one thing.
股價因減稅承諾而飆升是一回事。
The idea that investors believe another Trump presidency will make financial markets less risky is harder to fathom.
但投資者認為特朗普再次當選總統會降低金融市場的風險，這種觀點就更難以理解了。
Mr Trump threatens to widen a fiscal deficit that already yawns, impose tariffs reminiscent of those in the 1930s and undermine an international order that provides a foundation for firms’ supply chains.
特朗普威脅要擴大已經很大的財政赤字、征收與20世紀30年代相似的關稅，并破壞為企業供應鏈提供基礎的國際秩序。（注：30年代為應對經濟大蕭條，美國把關稅提高到歷史最高水平。）
Perhaps investors’ returns will be stellar in spite of all that.
或許盡管存在所有這些問題，投資者的回報仍將是出色的。
Few, though, think their risk of losses has ebbed away, and even fewer that the world has just become a more predictable place.
但很少有人認為自己的損失風險已經消退，更少有人認為世界已經變得更加可預測。
Instead, this is a rare moment in which the differences between volatility and risk—concepts investors often use interchangeably—are crystal clear.
相反，這是一個罕見的、波動率和風險（投資者經常互換使用這兩個概念）之間的差異非常清晰的時刻。
Volatility is a tightly defined calculation.
波動率是一種嚴格定義的計算。
It is the standard deviation of price fluctuations expected over a set timeline (30 days for the MOVE and the VIX), assuming they are distributed along a bell curve and that options are priced accordingly.
是在給定時間線（MOVE指數和VIX指數均為30天）內預期價格波動的標準偏差，假設的是價格波動沿著鐘形曲線分布，并且期權是據此定價的。
If, say, an election falls within the chosen timeline, the volatility of affected asset prices will duly rise to account for the difference in possible outcomes.
比如說，如果一場選舉發生在選定的時間線內，那么受影響資產價格的波動率將相應上升，以反映各種可能結果之間的差異。
It will then fall once the outcome is known and prices themselves have incorporated it.
一旦選舉結果揭曉，價格本身也已經包含了這一結果，那么波動率就會下跌。
Volatility is therefore an excellent tool for modelling some of the randomness that drives financial markets.
因此波動率是用于模擬一些驅動金融市場的隨機性的絕佳工具。
Some, but not all.
能模擬一些，但并非全部。
In reality, the randomness of both markets and the world they reflect is wilder than this.
在現實中，市場的隨機性和市場所反映的世界的隨機性比模擬的結果還要瘋狂。
Extreme events (think of wars, financial crises or pandemics) occur far more often than a well-behaved bell curve would suggest.
極端事件（想想戰爭、金融危機或大流行病）的發生頻率遠遠高于一條規規矩矩的鐘形曲線所顯示的頻率。
It is often impossible to attach a distribution of probabilities to their potential outcomes, or even to specify the full range of these.
通常情況下，我們無法確定這些事件的各種潛在結果會有什么樣的概率分布，甚至無法確定這些結果的全部范圍。
They certainly don’t come with tightly defined timelines.
而且事件當然不會有嚴格定義的時間線。
An instinctive understanding of risk allows for this wild randomness in ways that a statistical measure such as volatility cannot.
對風險的本能性理解會把這種瘋狂的隨機性計算進去，而諸如波動率之類的統計指標是無法計算的。
That is especially true for options traders, who, if asked for a contract insuring against too extreme a move, will simply name a price high enough to dissuade the buyer.
這對期權交易者來說尤其如此，如果他們被要求簽訂一份防止價格波動過于極端的合同，他們就會直接報出一個足以讓買家望而卻步的高價。
Investors, in other words, do not think Mr Trump’s presidency will be predictable.
換句話說，投資者并不認為特朗普的總統任期是可預測的。
They think its unpredictability is unpriceable.
他們認為其不可預測性是無法計算入價格的。
