THE dollar's tumble this week was attended by predictable shrieks from the markets; but as it fell to a 20 month low of $1.32 against the euro, the only real surprise was that it had not slipped sooner. Indeed, there are good reasons to expect its slide to continue, dragging it below the record low of $1.36 against the euro that it hit in December 2004.
　　The recent decline was triggered by nasty news about the American economy. New figures this week suggested that the housing market's troubles are having a wider impact on the economy. Consumer confidence and durable goods orders both fell more sharply than expected. In contrast, German business confidence has risen to a 15 year high. There are also mounting concerns that central banks in China and elsewhere, which have been piling up dollars assiduously for years, may start selling.
　　Yet cyclical factors only partly explain why the dollar has been strong. At bottom, its attractiveness is based more on structural factors-or, more accurately, on an illusion about structural differences between the American and European economies.
　　The main reason for the dollar's strength has been the widespread belief that the American economy vastly outperformed the world's other rich country economies in recent years. But the figures do not support the hype. Sure, America's GDP growth has been faster than Europe's, but that is mostly because its population has grown more quickly too. Dig deeper and the difference shrinks. Official figures of productivity growth, which should in theory be an important factor driving currency movements, exaggerate America's lead. If the two are measured on a comparable basis, productivity growth over the past decade has been almost the same in the euro area as it has in America. Even more important, the latest figures suggest that, whereas productivity growth is now slowing in America, it is accelerating in the euro zone.
　　So, contrary to popular perceptions, America's economy has not significantly outperformed Europe's in recent years. And to achieve this not much better than parity, America has had to pump itself full of steroids. Since 2000 its structural budget deficit (after adjusting for the impact of the economic cycle) has widened sharply, while American households' saving rate has plunged, causing the currentaccount deficit to swell. Over the same period, the euroarea economies saw no fiscal stimulus and household saving barely budged.
　　America's growth, thus, has been driven by consumer spending. That spending, supported by dwindling saving and increased borrowing, is clearly unsustainable; and the consequent economic and financial imbalances must inevitably unwind. As that happens, the country could face a prolonged period of slower growth.
　　As for Europe, the old continent is hobbled by inflexible product and labour markets. But that, paradoxically, is an advantage: it means the place has a lot of scope for improvement. Some European countries are beginning to contemplate (and, to a limited extent, undertake) economic reforms. If they push ahead, their growth could actually speed up over the coming years. Once investors spot this, they are likely to conclude that the euro is a better bet than the dollar.

　　这周，因为可预见的市场缩小，美元保持了下降的趋势。随着美元汇率下降到二十个月来的最低点（$1.32比1欧元），唯一可以算得上令人惊讶的恐怕是对于美元未来前景的悲观预测。有充分的理由令人相信美元的下降趋势将继续下去，甚至打破2004年十二月创造的$1.36比1欧元的历史最低点。
　　近期关于美国经济的大量负面新闻可以说是美元持续贬值的主要诱因。这一周来的新数据显示，美国房市的问题对经济带来了全局性的影响。消费者信心指数和耐用品订单量都显示了比预期中更严重的下滑。另一方面，德国商业信心指数创下了历史新高，而中国中央银行的近期言论更令人猜测其政策开始从囤积美元向出售美元倾斜。
　　但是，运用周期性因素去解释美元在历史上的上佳表现已经被证明是片面的了。美元对投资者的吸引力很大程度上基于经济结构要素--或者更准确地说，投资者对于美国和欧洲的经济结构差别的错觉。
　　美元过去强势的主因是大多数投资者认为：在近几年内，相对与其他富裕国家，美国经济的整体表现十分出众。但数据显示这种观念是错误的。的确，美国的国民生产总值增长速度要高于欧洲国家，但是这主要归功于美国快速增长的人口总量。对经济数据的更深层思考显示欧美经济差异并没有表面数据显示的那样大。生产力增长的官方数据虽然在理论上是影响货币汇率走向的重要指标，但实际上却夸大了美国的领先地位。如果将欧美放在同一指标上进行忽略其地缘及人口增长的公平比较，过去十年里欧美的经济表现基本上是同样的。更重要的是，最新的数据显示，当前美国的生产力增长正在放缓，而欧元区的生产力增长则在加速。
　　因此，和流行的观念恰恰相反，美国经济今年的整体表现并不明显强于欧洲的同期经济整体表现。同时，美国经济数据含水量丰富。自2000年以来，美国的结构性财政赤字显著提高（对经济周期对财政状况的影响进行修正后）。同时，随着美国家庭储蓄率持续下降，美国的流动资金赤字迅速增长。而在同一时期，欧元区的各经济体的财政状况良好，而家庭储蓄也基本保持不变。
　　美国的经济增长，在过去的一段时间里被消费增长所拉动。而消费增长则是建立在储蓄下降和负债增多的基础上的。很明显，这种形式的经济增长是无法持久的，而因之造成的经济以及财政的不平衡的后果也将不可避免的出现。随着这种消费主因的经济增长的消退，国家将可能面对长时间的经济增长放缓。
　　就欧洲而言，这块年迈的大陆被缺乏弹性的产品和劳工市场拖得步履阑珊。但是，虽然听起来有些荒谬，这种状况相对来说可能是一种优势：它意味着欧洲人有很大的空间去改善他们的经济状况。一些欧洲国家开始慎重考虑（并在小范围内试行）他们的下一轮经济改革。如果这些改革成功，他们的经济增长将在未来显著加快。一旦投资者发现这点，他们很可能认为欧元相比美元将是更加有利的选择。