美元主場：振作點--全球貿易依賴美元因而減少其益處

Greenback dominance: Buck up.

美元主場：振作點

Global trade’s dependence on dollars lessens its benefits

全球貿易依賴美元因而減少其益處

Policymakers around the world yearn to be free of the greenback’s grip

世界各地政策制定者渴望擺脫美元的束縛

Schools brief

Aug 27th 2020 edition

Aug 27th 2020

Crashing currencies hurt. They make imports more expensive, cutting into household budgets and raising businesses’ costs. But economics has long held that this pain brings with it its own salve. More expensive imports should drive new demand for home-made replacements and thus for the workers who make them, geeing up the economy. What is more, a devalued currency means exports are suddenly cheaper to buyers abroad. That, too, should boost demand. When the value of the Colombian peso collapsed in the summer of 2014, it was on the basis of these assumptions that the country’s finance minister greeted the fall as “a blessing in disguise”.

貨幣崩跌很傷。它使進口更加昂貴、侵蝕家庭預算，並增加企業成本。但是經濟學長期主張，這種痛苦附帶自我緩解。舶來品更昂貴，應能激起對國產替代品及其製造勞工的新需求，進而催動經濟。而且，貨幣貶值意味出口貨物對國外買家突然變便宜，這也應該能助長需求。哥倫比亞貨幣披索2014年夏天暴跌時，哥國財政部長正是基於這些假設，將匯率下跌視為「變相的祝福」。

It wasn’t. There were, the IMF opined in a subsequent report, a number of reasons for this, many specific to Colombia. But one problem was a factor which is embedded in the machinery of today’s international commerce. Colombia does not trade in pesos. It trades almost exclusively in dollars; 98% of its exports are invoiced in them. This is an extreme example of a general point. The amount of trade carried out in American dollars vastly exceeds the amount that America imports and exports. Although that may seem like a detail of book-keeping, it matters a lot. A growing body of evidence suggests that the dollar’s prominence in trade undermines the advantages which flexible exchange rates are meant to offer. And when the dollar strengthens, global trade tends to contract.

但它不是祝福。國際貨幣基金（ IMF）在隨後的報告中指出，這是多種因素造成，其中許多為哥倫比亞所特有。但問題是，有個因素嵌入當今國際商務機制。哥倫比亞對外貿易不用披索，幾乎只用美元，98％的出口都以美元計價。這是共通問題的一個極端例子。以美元進行的貿易額，遠大於美國的進出口額。儘管這似乎只是簿記的一個細節，卻極為重要。愈來愈多證據顯示，美元在貿易的重要地位，破壞彈性匯率理應提供的優勢。一旦美元走強，全球貿易趨於萎縮。

For decades, economists’ thinking about trade and currencies was summarised in a model created in the 1960s by two researchers at the IMF, Robert Mundell and J. Marcus Fleming. They assumed no special role for any dominant currency, but rather that traders would agree on prices in the exporter’s currency. A Colombian devaluation, say, would immediately turn peso-priced batteries into bargains abroad, encouraging foreign buyers to scoop up more of them. Meanwhile shoppers in Bogotá wanting to buy Brazilian T-shirts would resent being made to fork out more pesos to cover the price fixed in real.

兩位IMF研究員孟代爾（Robert Mundell）和佛萊明（J. Marcus Fleming）在1960年代創建的模型，總結了幾十年來經濟學家對貿易和貨幣的思考。他們假設，沒有任何主導貨幣承擔特殊角色，而是貿易商議定以出口方貨幣支付的價格。比方說，哥倫比亞貨幣若是貶值，以披索計價的電池立刻在國外變成便宜貨，鼓勵外國買家擴大收購。同時，波哥大的購物者若想買巴西T恤，可能埋怨被迫掏出更多披索來補足以里爾（巴西幣）訂的售價。

This simplifying assumption was potentially consequential. As early as 1947, Joan Robinson of the University of Cambridge noted that the currency companies used for invoicing could mute the expenditure-switching effect. If the prices of Colombian exports were in dollars, not pesos, a devaluation would leave prices faced by American importers—and their demand—unaffected. But though that might matter in principle, did it matter much in practice?

這種簡化的假設可能產生重要的影響。早在1947年，劍橋大學的羅賓遜（Joan Robinson）指出，簽發匯票的換匯公司可能會削弱支出轉換的效果。如果哥倫比亞出口以美元計價，而不是披索，那麼哥幣貶值對美國進口商與其需求來說，價格不受影響。但是，儘管那在原則上可能很重要，實務上是否也很重要?

In 1973 Sven Grassman of the Institute for International Economic Studies used Swedish data to answer in the negative. He found that in 1968 around two-thirds of Swedish trade had been indeed invoiced in the currency of the exporter. This “fundamental symmetry in international payment patterns” became known as “Grassman’s Law”. Swedish exports to America, which were mostly invoiced in dollars not kronor, were written off as the exception. That suggested that Mundell and Fleming were right.

1973年，國際經濟所的格拉斯曼（Sven Grassman）研究瑞典的數據後，做出否定的回答。他發現在1968年，瑞典約三分之二的貿易確實是以出口商的貨幣計價。這種「國際支付方式的基本對稱性」被稱為「格拉斯曼法則」。瑞典對美國的出口大多以美元計價，而非克朗。這表明孟代爾和佛萊明是正確的。

Over the next decades more data further supported Grassman’s Law—always with the same American exception. But by the 1990s some researchers were beginning to doubt its validity. Their main argument was that the actual prices of goods did not vary as much or as quickly as would be expected if payments were in fact symmetrical. Grassman’s Law said that the price of Brazilian T-shirts in Colombian markets should vary with the peso-real exchange rate, for example. But such prices were in fact much stickier.

往後幾十年，更多的數據進一步支持了格拉斯曼法則—--美國始終是特例。但是到1990年代，一些研究人員開始懷疑其有效性。他們的主要論點是，如果付款實際上是對稱的，商品實際價格的變化不會如預期的那樣大或快。舉例來說，按格拉斯曼法則，以哥倫比亞市場上巴西T恤的價格，應該隨著披索/里爾的匯率而變化。但這些價格實際上更加黏著不動。

In the mid-2000s Linda Goldberg and Cedric Tille of the Federal Reserve Bank of New York compiled data describing 24 countries in the late 1990s and early 2000s. This confirmed that Grassman’s Law was wrong: exports were not generally priced in the currency of the country they came from. In 2001, for example, they found that South Korea invoiced 82% of its imports in dollars, despite only 16% of its imports coming from America.

在2000年代中期，紐約聯邦準備銀行的戈柏（Linda Goldberg）和蒂爾（Cedric Tille）匯編1990年代末和2000年代初描述24國的數據，這證實格拉斯曼法則是錯的：出口產品通常不以出口國的貨幣計價。例如在2001年，他們發現，韓國82％的進口以美元計價，儘管只有16％的進口貨物來自美國。

Other work confirmed and updated their findings: the dollar has a huge role as a “vehicle currency” in which to invoice transactions to which no Americans are party, particularly in developing countries. Gita Gopinath of the IMF has compiled data covering just over half of world trade to show that the dollar’s share of invoicing was 4.7 times larger than America’s share of the value of imports, and triple its share of world exports. Another IMF study showed that the dollar’s share has not decreased in step with America’s declining share of overall trade.

其他研究也證實並更新他們的發現：即使沒有美國人參與匯票貿易，美元仍扮演著重大的「媒介貨幣」角色，特別是在發展中國家。IMF的戈皮納特（Gita Gopinath）匯整涵蓋全球逾半數貿易的數據，顯示美元的匯票額占比，較美國的進口額占比高4.7倍，且為美國占世界出口額比率的三倍。 IMF另一項研究顯示，美國在整體貿易的占比下降，但美元貿易額占比未隨著同步減少。

The euro’s creators had hoped that it might supplant the dollar’s status. But even though almost half of trade is invoiced in euros, that is mostly because of how much trade involves countries that use the currency. Between 1999 and 2014 euro-denominated trade was only around 1.2 times the euro zone’s share of global imports.

歐元的創造者曾希望藉此取代美元的地位。但即使近半的貿易以歐元支付，這也大部分是因為使用歐元的國家涉及如此多的貿易。從1999年到2014年，以歐元計價的貿易僅是歐元區占全球進口額的1.2倍左右。

Other would-be challengers appear to have failed even more miserably. Scant Chinese data suggest that in 2013 only 17% of Chinese trade was settled in renminbi, and in 2012 only around half of such settlements were invoiced in renminbi. In order to avoid financial sanctions, Russia has recently shifted away from the dollar when paying for imports from China. But the euro, not the renminbi, benefited most.

其他可能的挑戰者似乎輸得更慘。寥寥無幾的中國數據顯示，2013年中國貿易僅17％用人民幣結算，而在2012年，此類結算只有大約一半是用人民幣支付的。俄羅斯為避免金融制裁，最近給付自中國進口的費用時已避免用美元。但是受益最大的是歐元，而非人民幣。

A lack of historical data makes it impossible to say whether Grassman’s Law held in the 1970s and has since weakened or whether it was the always an artefact of insufficient data. Whichever is true, economists busied themselves trying to work out why exporters used dominant currencies.

由於缺乏歷史數據，無法確定「格拉斯曼法則」究竟是只適用於1970年代，然後適用性減弱，還是該法則始終只是數據不足造成的假象。無論哪種說法為真，經濟學家還在忙著弄清楚，為什麼出口商使用主流貨幣。

One suggestion is that using the same vehicle currency when setting prices for a certain market lets companies avoid erratic price movements relative to their competitors. Ms Goldberg and Mr Tille offered some support for this when they showed that dollar invoicing was more common in markets, such as precious metals, where competition is cut-throat. Another suggestion is that the rise of global supply chains saw more exporters importing some inputs. Invoicing imports and exports in the same currency would preserve their profit margins in the event of a devaluation.

一個可能的解釋是，使用同一媒介貨幣在特定市場設定價格，公司相對於對手可避開不穩定的價格波動。戈柏和蒂爾提供了一些支持證據，如在貴金屬等競爭激烈的割喉市場中，美元支付更為普遍。另一個解釋是，全球供應鏈的興起，使更多出口商進口相同的原料。進出口貨物都以相同貨幣計價，萬一貨幣貶值，即可保住利潤。［對照這句原譯：如果進出口出現貶值，以相同貨幣支付將保住利潤。］

The arguments for a vehicle currency do not necessarily mean that that currency has to be the dollar. But why would it not be? The dollar already dominates the financial world. Central banks stash 58% of their official foreign-exchange reserves in it. It is the global currency of choice when issuing securities. Banks use it for around half of their cross-border claims. According to SWIFT, a payments system, it is used in two-fifths of international payments.

關於媒介貨幣的論點，並不一定意味著這貨幣必須是美元。但是為什麼不呢？美元已經主導金融世界，央行58％的官方外匯準備是美元，它是發行證券時的首選全球貨幣。也用於銀行大約一半的跨境索賠。根據付款系統SWIFT的說法，美元約用於五分之二的國際付款。

Indeed the worlds of finance and trade are intertwined. Exporters borrowing in dollars will want to price their foreign sales in the same currency, to protect against a sudden devaluation which would increase the value of their debt. Assets denominated in dollars offer their owners more security, because they will hold their value relative to imports priced in dollars.

事實上，金融和貿易世界是密不可分的。出口商借入美元，是想以相同貨幣對國外銷售進行定價，以防止突然貶值而債務增加。美元計價的資產為持有者提供更大的安全性，因為比起美元計價的進口產品更能保值。

Having established the importance of dollar dominance for global trade, economists updated their understanding of exchange-rate gyrations. In America sticky prices set in dollars mean the demand for imports is impervious to exchange-rate shocks. A Colombian light aircraft priced at $50,000 will cost the same when the dollar is worth 3,000 pesos as when it is worth 4,000. The change will eventually have an effect—but it will be partial, and slow. One study has found that two years after an exchange-rate shift only 44% of its effect would be seen in prices in America. Another found that just as prices did not change much, neither did the volumes importers chose to buy. After a 1% dollar depreciation, they found that the volume of imports into America fell by a measly 0.003%.

在確立美元主導地位對全球貿易的重要性後，經濟學家們更新對匯率波動的理解。在美國，價格緊黏著美元，意味著進口需求不受匯率衝擊的影響。一架定價50,000美元的哥倫比亞輕型飛機，不論美元匯價是兑3,000元披索或兑4,000元披索，售價都一樣。改變最終會產生影響，但將是局部且緩慢的。一項研究發現，匯率大幅變動兩年後，只有44％的影響會反映在美國物價上。另一個發現，一如價格沒有太大變化，進口商選擇購買的數量也沒多大影響。在美元貶值1％之後，他們發現，美國的進口量僅下降區區0.003％。

Money, money, money 錢錢錢

All this allows America to enjoy what Ms Gopinath describes as a “privileged insularity”. Its adjustment to a dollar depreciation happens almost entirely through exports, which immediately become cheaper in foreign markets. Devaluations against the dollar in other countries, by contrast, see them suffer. It becomes harder to afford imports while they don’t get the added export oomph the old models suggested. Exporters’ dollar earnings will be worth more in local currency, which might tempt some of them to expand. But that takes time. And the benefits are often offset by the higher cost of imported inputs.

所有這些使美國能夠享受戈皮納特所說的「特權的孤立」。美國對美元貶值的調整，幾乎全透過出口進行，而出口產品在外國市場立即變得便宜。相形之下，其他國家的貨幣對美元貶值，則使這些國家受苦。進口愈來愈難買得起，出口也未像舊模型所示那樣為之一振。出口商的美元收入以本地貨幣計價更值錢，這可能誘使其中一些業者擴大規模。但這需要時間，況且收益常被進口原料成本升高抵消。

Around the world invoicing imports in dollars means that it is devaluations against the greenback, rather than against the currency of the country you are trading with, that count. Emine Boz of the IMF, Ms Gopinath and Mikkel Plagborg-Muller of Princeton University found that prices of imported goods were relatively unresponsive to bilateral exchange-rate movements. 

Over short-term horizons they were six times more sensitive to the dollar exchange rate. The price of Brazilian-made football shirts in Mexico will stay the same if the peso depreciates relative to the real, but not relative to the dollar. If the peso drops with respect to the dollar, though, those shirts will become less affordable and may no longer be sold.

全球各地進口商品以美元計價，意味對美元貶值才茲事體大，對貿易對手國貨幣貶值並不要緊。 IMF的博茲（Emine Boz）、普林斯頓大學的戈皮納特（Gopinath）和馬勒（Mikkel Plagborg-Muller ）發現，進口物價對雙邊匯率變動相對沒有反應。短期內，它們對美元匯率的敏感性高六倍。如果披索對里爾貶值但未對美元貶值，墨西哥賣的巴西製足球衫價格將保持不變；但若披索對美元貶值，這些襯衫將變得更難買得起，甚至不再出售。

During the East Asian crisis of 1997-99 South Korea, Malaysia and Thailand all experienced currency depreciations of at least 60% relative to the dollar—and saw their export volumes stagnate or fall. With prices set in dollars devaluations did nothing for their export competitiveness within the region. And demand for imports from elsewhere in the region—also priced in dollars—plunged. Ms Boz and her co-authors have found that, after accounting for the business cycle, a 1% appreciation in the value of the dollar translates into a 0.6% decrease in the volume of trade between countries in the rest of the world.

在1997-99年的東亞金融風暴期間，南韓、馬來西亞和泰國的貨幣對美元至少貶值60％，而出口量不是停滯就是下降。以美元計物價下跌，對這些地區的出口競爭力毫無幫助，而從區內其他地方進口的需求（也以美元計價）也暴跌。博茲和她的合著者發現，在考量經濟周期之後，美元升值1％，意味著世界其他國家之間的貿易量下降0.6％。

Dollar dominance means trade is vulnerable to the global financial cycle, too. A study by Valentina Bruno and Hyun Song Shin of the Bank for International Settlements found that a dollar appreciation leads banks reliant on dollar funding to shrink their credit supply. Companies reliant on those banks—and their dollar-denominated financing of trade—then slow their exports, an effect particularly marked in companies with longer supply chains. Trade is a finance-hungry business.

美元支配地位意味著貿易也容易受全球金融周期的影響。國際清算銀行的布魯諾（Valentina Bruno）和申賢松（Hyun Song Shin）的研究發現，美元升值導致依賴美元資金的銀行縮減授信。依靠這些銀行取得美元計價貿易融資的公司，因此放慢出口腳步，這種影響在供應鏈較長的公司中尤其明顯。貿易是需要大量資金的業務。

Policymakers around the world yearn to be free of the dollar’s grip. That seems unlikely. The dollar’s dominance is the product of millions of individual decisions, each seemingly optimal, which in concert lead to collective problems. Each dip in the dollar’s value leads to a rush of wishful chatter about the dollar’s demise, but for long as these optimisations continue to make sense it is hard to see how that wish can come true. At least, though, for a while, the chatter-inducing weakness will provide a fillip to trade. ■

全球決策者渴望擺脫美元的束縛，這似乎不太可能。美元的主導地位是數以百萬計的個體決定下的產物，而每一個似乎都是最佳的決定，這些決定共同導致集體的問題。美元價值每下跌一次，都會引起人們一廂情願急著談論美元垮台，但只要這些最佳化措施仍有道理，就很難看出那種願望如何成真。至少有一段時間，引發議論紛紛的美元弱勢，將為交易提供興奮劑。 ■