美元為什麼跟赤字背離

Eric︰很多交易員剛進入市場時，常陷入一種基本面和市場相反的矛盾中，本文可稍微給你一點方向

金融時報 2006年1月19日 星期四

譯者/張征

The Belgian chocolate theory of the dollar

美元匯率為何與赤字背離

A year ago, most analysts agreed: the dollar could only go down against the euro and the other main currencies. The huge US current account deficits had become unsustainable and called for a big decline of the dollar. A year later these analysts proved to be wrong. The dollar went up by close to 15 per cent against the euro. What went wrong? Let me answer the question by telling a story about Belgian chocolates.

一年前，大多數分析師都同意：美元兌歐元與其它主要貨幣只會下跌。美國已無法支撐其巨額經常賬戶赤字，美元需要大幅貶值。一年後，事實證明這些分析師都錯了。美元兌歐元上升了近15%。出了什麼問題？我說一個有關比利時巧克力的故事來回答這個問題。

A few weeks ago an interesting experiment was undertaken at the Brussels food fair, a yearly affair where food lovers wander around among the many stalls stuffed with all imaginable delicacies. A shop was put up selling boxes of Belgian chocolates. The first day the price was set at €9 for each box. Sales went well. The next day the price was raised to €15 per box. Steeped in economic theory, you might think that demand now declined. Wrong. Demand doubled. On the third day the price was lowered to €2 for each box. Demand for chocolates collapsed. What went wrong with the law of demand?

幾周前，布魯塞爾食品展上進行了一個有趣的實驗。在這個一年一度的食品展上，攤位裡擺滿了各種你能想到的美食，而美食愛好者則在許多攤位之間來回穿梭。其中一間搭好的攤位在銷售盒裝比利時巧克力。第一天，巧克力的售價定在每盒9歐元，生意不錯。第二天，價格上漲到了每盒15歐元。假如你飽讀經濟理論，可能會認為需求現在會下降了。錯。需求翻番了。第3天，價格降至每盒2歐元，對巧克力的需求一落千丈。需求法則出了什麼問題？

The explanation is given by psychologists. It is very difficult, if not impossible, for the consumer to find out the quality of chocolates by just looking at their appearance in the shop. When confronted with such uncertainty about the intrinsic value of things, consumers use simple rules of thumb that they understand. Psychologists call these 「heuristics」. In this case, the price of the chocolates provides the rule of thumb.

心理學家對此給出了解釋。消費者即便有可能，也很難在店裡僅憑巧克力的外表來判斷它們的質量。當消費者對事物的內在價值如此不確定時，就會用他們了解的、簡單的經驗法則。心理學家稱之為「探索法」。在上面的例子裡，巧克力的價格就是經驗法則。

Most consumers have some experience that allows them to associate high price with high quality. It is not always like that, but on average it probably is. Thus when looking at the €15 box the consumers infer that the high price reflects high quality and they buy the chocolates. Consumers who see the boxes priced at €2 infer that the quality of these chocolates is not to be trusted, and they do not buy them. The law of demand is turned upside down.

大多消費者都有某些經驗，會讓他們把高價格與高品質聯系起來。事情並非總是如此，但一般而言可能如此。因此，當看到每盒售價15歐元的巧克力時，消費者推斷這個高價反映了高質量，然後就買下了巧克力。當看到每盒標價2歐元的巧克力時，消費者推斷這些巧克力的質量不能讓人放心，所以他們沒有去買。需求法則完全顛倒了。

Let us now return to the dollar. Most people dealing in the foreign exchange market have no clue about the fundamental value of the dollar (the 「quality」 of the dollar). Specialists and professors do not know either, at least within a broad range of dollar-euro rates between say, $1.0 and $1.3. For every specialist telling us that the fundamental value of the dollar is close to $1.3 to the euro there will be another one affirming that $1.0 is near the fundamental value. Anything in between is fair game. Faced with such uncertainty, traders in dollars and euros have no way of knowing. They will therefore use a rule of thumb, an easy guide that they understand. The market price of the dollar provides such a rule of thumb. Thus when the dollar goes up for some technical reason, or just by chance, the increasing dollar is a signal for people that there must be some hidden economic strength driving the dollar. And they buy dollars; like the Belgian chocolate lovers buy chocolates when they are highly priced. Conversely, when the dollar moves down for whatever reason, people interpret the decline of the dollar as reflecting a fundamental weakness of the dollar, and they sell dollars.

現在讓我們來看看美元。大部分在外匯市場進行交易的人，對美元的基本價值(美元的「質量」)沒什麼頭緒。專家和教授們也不知道，至少在美元兌歐元的大區間裡是如此，比如在1.0美元到1.3美元之間。每當有專家告訴我們，美元對歐元的基本價值接近1.3美元，總會有另一個專家斷言，基本價值接近1.0美元。而兩者間的任何數字都會有人選擇。面對這樣的不確定性，美元與歐元的交易商都無法得知確切情況，因此，他們就會使用他們所了解的簡單指導——經驗法則。美元的市場價格就是這樣的經驗法則。當美元出於某個技術原因上漲(或偶然上漲)時，不斷上漲的美元就是給人們的信號，說明必然有某種隱藏的經濟力量在推動美元。所以他們買進美元，就像比利時巧克力的愛好者在高價時買巧克力一樣。相反，當美元出於這樣那樣的原因走低時，人們把美元的下跌解讀為反映了美元的基本弱勢，因此他們拋售美元。

As a result of this mechanism, the dollar moves up and down within upper and lower bounds that are determined by our lack of knowledge of the fundamental value of the currency. These movements may or may not be caused by changes in the variables (such as the current account) that influence the fundamental value of the dollar.

作為這一機制的結果，美元在上下限越來越大的區間裡浮動，這是我們對美元的基本價值缺乏了解所造成的。這些浮動可能是由影響美元基本價值的變量(比如經常賬戶)變化造成的，也可能不是。

There is a difference, though, between Belgian chocolates and the dollar. The Belgian chocolate lover buying high-priced chocolates can immediately check the quality by tasting the chocolates. The buyer of dollars cannot. But he is in need of a justification of his buy as a good one. And here the analyst comes in handy.

但比利時巧克力和美元之間也有不同之處。高價購買巧克力的比利時巧克力愛好者，可以馬上嘗一口巧克力以檢驗品質。而美元買家卻不行，但他需要證明，他買得很好，於是分析師就派上用場了。

The analyst, who does not know more about the fundamental value of the dollar than the unsuspecting buyer, invents stories. Thus when the dollar goes up, the analyst goes on a search for variables that move in the right direction and that can be linked to the rising dollar, carefully eliminating from the analysis all the other fundamental variables that move in the wrong direction. And so we are told that the strength of the dollar last year was due to interest rate differentials favouring the dollar. The further widening of the current account deficit, which in a previous analysis got centre stage, is carefully dropped from the new analysis.


對於美元的基本價值，分析師並不比毫無戒心的買家了解得更多，所以他們就編故事。因此，當美元上漲時，分析師就去尋找走向正確的變量，以及可以和美元上漲聯系在一起的變量，並謹慎地從分析中去掉所有走向錯誤的其它基本變量。所以我們被告知，去年美元的強勢是由於利差有利於美元。在上一次的分析中，進一步擴大的經常賬戶赤字是關注的中心，而在新的分析中卻被小心翼翼地剔除掉了。

The honest story of why the dollar increased last year is that we simply do not know. But we do not like to admit that we do not know. Our psyche abhors the darkness of ignorance. That is why analysts』 services continue to be demanded. They fulfil a psychological need to understand. Exchange rate economics these days satisfies this need by telling a new story each time the dollar goes up or down.

我們的確不知道去年美元為何上漲的真相，但我們就是不想承認我們不知道。我們打心眼裡痛恨茫然無知。那就是分析師的服務不斷有需求的原因。他們滿足了人們了解真相的心理需要。如今，每當美元上漲或下跌，匯率經濟學就會編一個新故事以滿足這種需求。

What does that tell us about the coming year? You may now be concluding that the sceptical tone of this column does not leave me much scope to say something useful. Yet I do think that the cumulated force of increasing US current account deficits and debts will be overwhelming, bringing down the dollar. But do not ask me when this will happen.

關於新的一年，它給我們的啟示是什麼？你現在可能推斷說，這個專欄的懷疑論調，沒給我留下多少空間來說些有用的東西。然而我確實認為，美國日益增長的經常賬戶赤字和債務的累積力量將是無法抵抗的，它會拖低美元，但別問我是什麼時候。

\The writer is professor of economics at the University of Leuven

作者是比利時魯汶大學(University of Leuven)經濟學教授。