美联储的美元大赌局

    落健生发液（Rogaine）和美国联邦储备委员会（Federal Reserve，简称美联储）的经济刺激政策有什么共同点？请不要往本•伯南克和艾伦•格林斯潘的发际线这个方向去考虑。想不出来了吧？答案是：副作用。

    正如您可能知道的，落健生发液最初是作为血压药开发的，但后来“更改用途”，因为它有促进头发生长的副作用。今天我们将讨论美联储的两大副作用——与一些主要贸易伙伴的潜在货币战以及降低联邦预算赤字。虽然落健生发液更为家喻户晓，但是美联储两大副作用要比生发液重要得多。作者没有任何冒犯秃头男性的意思。

    美联储的第一个副作用，即货币战争，表明通过降低利率来刺激经济这种好事可能也有弊端。由于美联储降息比大多数其他央行来得更快且幅度更大，导致美元兑许多主要贸易伙伴国货币的汇率走软。当然，美联储并没有大张旗鼓地向公众表示它乐意看到这样的局面。但事实正是如此，因为美元逐渐贬值会使美国的出口产品更便宜，而进口自他国的产品变得更昂贵，这样一来就会促进美国本土的就业增长。

    问题是，如果所有国家都寻求本币贬值，大家都不会得到好处。【事实上，在80年前的大萧条（Great Depression）出现前，这个问题就曾一度抬头。】而且，不仅没有好处，相关经济体还会面临广泛的不稳定性、恐惧和贸易战争。对于这种可能性，即使像我这样的先天乐天派都会感到有一点点紧张。

    读者可以从下图看出，自2009年以来，美元兑主要贸易伙伴国货币的汇率已下跌超过10%。正是在国际金融危机全面爆发的2009年，美联储推出了一个又一个的计划，以期压低利率。尽管美元可能在2009年处于虚高水平，但它随后的下跌对贸易产生了重大影响。

    What do Rogaine and the Federal Reserve's economic-stimulus policies have in common? No, it doesn't involve Ben Bernanke's or Alan Greenspan's hairlines. Give up? The answer: side effects.

    Rogaine, as you may know, was originally developed as a blood pressure medication but was "repurposed" because it had the side effect of promoting hair growth. The two Fed side effects we'll discuss today -- prospective currency wars with some major trading partners, and a reduction in the federal budget deficit -- are far less known than Rogaine's. But, with all due respect to follicularly challenged males, they're a lot more important.

    The first Fed side effect, currency wars, is an example of how something good -- stimulating our economy by lowering interest rates -- can have a downside. Cutting interest rates faster and more deeply than most other central banks has weakened the dollar against the currencies of many of our major trading partners. The Fed doesn't exactly run around telling the public that it's happy to see this happen. But that's the case, because a gradually declining dollar encourages job growth in our country by making our exports cheaper and our imports more expensive.

    The problem, which reared its head in the run-up to the Great Depression 80 years ago, is that if everyone devalues, no one benefits. Instead, you get widespread instability, fear, and trade wars. The prospect of that makes even a congenital optimist like me more than a little nervous.

    You can see from the chart below that the dollar has dropped more than 10% against the currencies of our major trading partners since 2009, when the world financial crisis was in full swing and the Fed invented one program after another to drive down interest rates. The dollar may well have been artificially high in 2009, but nevertheless, its subsequent decline has had a major impact on trade.