AT THE start of 2017, just before Donald Trump was inaugurated as president, a survey of fund managers by Bank of America Merrill Lynch (BAML) found they believed that being positive on the dollar was “the most crowded trade”. It turned out they were right to be cautious. On a trade-weighted basis, the currency has fallen by 9% against other major currencies in the past year.

在2017年初，仅在唐纳德·特朗普（Donald Trump）宣誓就任美国总统之前，美银美林集团（Bank of America Merrill Lynch）对基金经理发起的一份调查显示，基金经理认为看好美元会是“最为热门的交易”。事实证明，他们的小心谨慎态度是正确的。按经贸易额加权的汇率来看，在过去的一年里，美元对其它主要货币的汇率下跌了9%。

It is not clear what the Trump administration thinks about this.  At the recent World Economic Forum in Davos, Steven Mnuchin, the treasury secretary, said: “Obviously a weak dollar is good for us as it relates to trade and opportunities.” Although the rest of his statement was more nuanced, it is unusual for anyone in his position to depart from a “strong dollar” line. The greenback duly fell in price.

特朗普政府对此作何看法还尚不清楚。最近在达沃斯举行的世界经济论坛（World Economic Forum）上，美国财政部部长史蒂文·努钦（Steven Mnuchin）说：“显然美元的疲软对我们 40 33835 40 13607 0 0 7437 0 0:00:04 0:00:01 0:00:03 7435有利，因为它和贸易与机遇紧密联系。”虽然他接下来的发言有更为细微的差别，但对于处在他这种职位的人来说， 偏离“强势美元”方针是不同寻常的事。美元价格也应声下跌。

Mr Trump then followed up with a statement in favour of a strong dollar in the long term, which caused a rebound. Since it was only last April that the president talked about the dollar being “too strong”, the markets can be forgiven for being confused. Never mind singing from the same hymn-sheet, the American authorities are using different tonal systems.

特朗普随后发表声明，称从长期来看是支持美元强势地位的，让美元的价格回升。就在去年四月，特朗普还在谈美元“太过于强势”，因此市场表现混乱是可以理解的。美国政府部门的口径各不相同，更不用说异口同声了。

Adding to the puzzle is the administration’s focus on eliminating the trade deficit.  The recent package of tax cuts, by boosting demand, is likely to suck in imports and widen the deficit. The trade deficit tends to fall during a recession, but that is not a desirable outcome. So it may need a big decline in the value of the dollar to bring about a cut in the deficit, while keeping the economy buoyant.

特朗普政府把焦点放在消除贸易逆差上，这更让人们迷惑不解。最近出台的一系列减税政策可能会刺激需求，从而吸引进口产品，拉大逆差。贸易逆差在经济衰退时常常会减少，但这一结果并不令人满意。因此，美元价格或许需要大幅下跌才能减少贸易逆差，同时保持经济的繁荣发展。

If the dollar is poised to experience one of its long periods of weakness, as in the late 1980s or the early 2000s (see chart), what would that mean for the financial markets? Much may depend on the reason the dollar is weak. If the weakness is related to bad news about the American economy, then that is usually bad for equities and good for government bonds. The reverse applies if the weakness reflects a boom in emerging markets; that would be a sign of investors taking advantage of exciting opportunities elsewhere.

如果美元准备好经历又一次的长期疲软，一如20世纪80年代末或21世纪初那样（见图表），对金融市场有何影响呢？影响将大大取决于美元疲软的原因。如果美元疲软和美国经济不景气有关，那这通常不利于股市，而有利于政府债券。如果美元疲软映射出新兴市场的繁荣，那结果将恰恰相反；这一迹象将表明投资者充分利用了其他地方的大好机遇。

Current dollar weakness seems to be linked to a rebound in the global economy. That also helps explain why stock markets have started 2018 in a buoyant mood. A weaker dollar helps American multinationals, as Mr Mnuchin suggested. Not only does it make their exports more competitive, but their overseas earnings are also worth more in dollar terms.  BAML says that, in the fourth quarter, 68% of companies with high foreign sales beat analysts’ forecasts of profits and sales. Only 39% of companies with no foreign exposure managed to do so.

当前美元走低似乎和全球经济的回暖有一定关系。这也可以用来解释为何股市在2018年开局就呈现出一派欣欣向荣之景。正如财政部部长努钦所言，美元走低有利于美国的跨国企业，不仅使得这些企业的出口产品更具竞争力，它们的海外收入换算为美元之后将更值钱。美银美林表示，在海外销售额高企的企业中，68%的企业在去年第四季度的利润和销售额超过了市场分析人士的预测。在没有外汇风险的企业中，做到的只有39%。

Although equities have been performing strongly, Treasury-bond prices have been falling (in other words, yields have been rising). This may suggest that foreign investors need a higher return to persuade them to put their money in a depreciating currency. Another explanation   is that American bond investors think stronger economic growth will eventually lead to higher inflation and are demanding higher yields to compensate (see next story).

虽然股市的表现一直以来都很强劲，长期国库券价格却一直在下跌（换言之，收益率一直在上涨）。这或许暗示着外国投资者需要有高收益率的刺激，这样才能说服他们把钱投在贬值的货币上。另一种解释是美国的债券投资者认为强劲的经济增长最终会导致更高的通货膨胀率，因此他们正强烈要求更高的收益率来补偿通货膨胀带来的损失。

What about the rest of the world? A weak dollar means a strong euro and thus, all else being equal, tighter financial conditions in Europe. Mario Draghi, the president of the European Central Bank, made some pointed remarks on January 25th about disorderly movements in exchange rates, and their adverse implications for financial and economic stability. He took a more doveish tone on monetary policy than investors expected; the ECB will not want the euro to rise too far. Government-bond yields in Europe have also been rising, so financial conditions are already tightening.

世界上其他国家的反应如何？美元走低意味着欧元走强，因此在其他条件等同的情况下，欧洲的金融环境将收紧。1月25日，欧洲中央银行（European Central Bank）行长马里奥·德拉吉（Mario Draghi）就汇率的无序调整以及这给金融和经济稳定造成的不利影响做出了尖锐的评论。出乎投资者的预料的是，他在货币政策上采取了更加鸽派的语调；欧洲中央银行不想让欧元涨得过高。欧洲的政府债券收益率也一直在上涨，因此金融环境在收紧了。

Life tends to be easier for economic policymakers in developing countries when the dollar is falling than when it is rising. The Asian financial crisis, for example, occurred during the dollar surge of the late 1990s. Many countries peg their currencies, formally or informally, to the greenback; if the dollar is rising, they may be forced to tighten monetary policy in order to maintain the link. A weaker dollar gives countries scope to cut interest rates, boosting growth.

相比于美元上涨，发展中国家的经济决策人在美元下跌时往往会更轻松一些。例如，上世纪90年代末，美元价格的飙升导致了亚洲金融危机。无论是正式地还是非正式地，很多国家都固定本国货币对美元汇率；如果美元上涨，它们将被迫收紧货币政策，以维持汇率不变。美元走低将为其他国家提供降低利息的机会，以刺激增长。

Of course, all these trends may go into reverse if they go too far. If a lot of money flows into emerging markets, economies can overheat and an overvalued currency can make exporters uncompetitive, leading to an eventual crisis. If Treasury-bond yields rise far enough, that will prompt capital to flow back into the dollar. Furthermore, a sharp rise in bond yields will put the squeeze on economic growth. Investors do not mind a bit of dollar weakness; they just don’t want too much of it.

当然，如果这些国家过犹不及，所有趋势都会向相反的方向转化。如果太多资金流入新兴市场，经济会过热，高估的货币会使出口产品不具备竞争力，最终导致危机出现。如果长期国库券收益率涨得过多，这将促使资本回流进美元。更有甚者，债券收益率的快速上升会对经济增长施加压力。投资者不介意美元稍微走低；他们只是不想它走低太多。

编译：ColletteYu

编辑：翻吧君

来源：经济学人（2018.02.03）