Adam Hayes 2015年9月3日
这个月，中国通过货币贬值震惊了世界并导致道琼斯工业平均指数进行了自2010年闪电崩盘以来最剧烈的下跌，在2015年8月24日开盘时下跌了1000点。人民币对美元下降了超过3.5%。这看起来不多，但是中国政府历来对美元执行严格的汇率控制。中国已经成为世界上第二大经济体，也是世界贸易的重要组成部分。
讽刺的是，多年来美国政府一直向中国施压贬值人民币，声称这使人民币在国际贸易中具有不公平的优势并人为控制资本和劳动力价格低廉。现在中国政府采取紧急措施贬值他们的货币，被指责成为全球市场带来不确定性。
这个最近的事件并不是什么新鲜事。自从全球货币放弃国际标准并允许他们互相之间自由浮动汇率，发生过许多货币贬值事件，不仅仅伤害涉及国家的居民，使全球都跟着波动。如果影响如此普遍，国家为什么对货币贬值呢？
促进出口
在国际市场中，来自一个国家的商品必须和来自全世界的商品竞争。美国的汽车市场必须和日本和欧洲的汽车市场竞争。如果欧元对美元贬值，欧洲制造商制造的汽车在美国以美元出售，将会比之前便宜的多。另一方面，货币价值更高则出口到外国的商品价格更昂贵。
换句话说，出口商在国际市场变得更有竞争力。鼓励出口打击进口。但是有一些值得注意的地方，因为两个原因。首先，当全世界都需求出口商的商品时，价格会上升，使贬值影响变得正常。第二点就是其他国家发现这种方式有效，他们就会被激励对他们的货币进行贬值。这将导致货币战争和无节制的通货膨胀。
缩小贸易赤字
由于出口变便宜进口变昂贵，出口增加，进口减少。这有利于改善国际收支，出口增加，进口减少，缩小贸易赤字。现在持续的赤字并不少见，美国和其他一些国家连续多年贸易失衡。然而经济理论认为贸易赤字是不可持续的，这将导致危险的债务水平并削弱经济。国内货币贬值可以帮助矫正国际贸易支出并削减赤字。
然而这种原理存在一个缺点。货币贬值也会增加外币计价的债务负担。这对使像印度和阿根廷这样拥有巨大金额美元和欧元债务的国家来说是个很大的问题。这些国外债务变得更加难以偿还，削减国内货币市场信心。
降低主权债务负担
如果政府有用大量的主权债务他们可能会出台弱势货币政策。如果还款是固定的，贬值将会使还款更加便宜。
比如政府每个月需要对未偿还债务支付100万美元的利息。但是如果这100万美元国际债务价值降低，这部分债务则更容易偿还。在我们的例子中，如果国内货币贬值到原来一半的价值，那么100万美元的债务就只值50万美元。
再次，这种策略需要小心使用。因为全球大多数国家都有各种形式的未偿还债务，这可能引起货币战争。这种策略在国家持有大量国外债券时也会失效，因为这将使这利息支付更加昂贵。
总结
货币贬值可以被国家用来实现经济政策。拥有比世界其他国家价值更低的货币将刺激出口，缩小贸易赤字和减少未偿还债务的利息支付。然而，货币贬值也有负面影响。他们在全球市场带来不确定性，可能导致市场下跌和刺激衰退。国家间可能会进入一个以牙还牙的货币战争。这是一个非常危险弊大于利的恶性循环。
3 Reasons Why Countries Devalue Their Currency
By Adam Hayes, CFA | Updated September 03, 2015
This month, China surprised world markets and spurred the most precipitous drop in the Dow Jones Industrial Average – falling more than 1000 points at the open of Monday August, 24 2015 – since the flash crash of 2010, by taking moves to devalue their currency. The Yuan is now down over 3.5% against the U.S. dollar over the past twelve months. This may not seem like a lot, but the Chinese government has traditionally held a strict peg to the dollar. The Chinese economy has become the second largest in the world, and is an integral component of global trade.
The ironic thing is that for many years, the United States government had been pressuring the Chinese to devalue the Yuan, arguing that it gave them an unfair advantage in international trade and kept their prices for capital and labor artificially low. Now that the Chinese are enacting emergency measures to devalue their currency, they are being blamed for bringing global uncertainty in markets. (For more, see: The Chinese Devaluation of the Yuan.)
This most recent event is nothing new. Ever since world currencies abandoned the gold standard and allowed their exchange rates to float freely against each other, there have been many currency devaluation events that have hurt not only the citizens of the country involved, but have also rippled across the globe. If the fallout can be so widespread, why do countries devalue their currency?
To Boost Exports
On a world market, goods from one country must compete with those from all other countries. Car makers in America must compete with car makers in Europe and Japan. If the value of the euro decreases against the dollar, the price of the cars sold by European manufacturers in America, in dollars, will be effectively less expensive than they were before. On the other hand, a more valuable currency make exports relatively more expensive for purchase in foreign markets.
In other words, exporters become more competitive in a global market. Exports are encouraged while imports are discouraged. There should be some caution, however, for two reasons. First, as the demand for a country's exported goods increases worldwide, the price will begin to rise, normalizing the initial effect of the devaluation. The second is that as other countries see this effect at work, they will be incentivized to devalue their own currencies in kind in a so-called "race to the bottom." This can lead to tit for tat currency wars and lead to unchecked inflation.
To Shrink Trade Deficits
Exports will increase and imports will decrease due to exports becoming cheaper and imports more expensive. This favors an improved balance of payments as exports increase and imports decrease, shrinking trade deficits. Persistent deficits are not uncommon today, with the United States and many other nations running persistent imbalances year after year. Economic theory, however, states that ongoing deficits are unsustainable in the long run and can lead to dangerous levels of debt which can cripple an economy. Devaluing the home currency can help correct balance of payments and reduce these deficits.
There is a potential downside to this rationale, however. Devaluation also increases the debt burden of foreign-denominated loans when priced in the home currency. This is a big problem for a developing country like India or Argentina which hold lots of dollar- and euro-denominated debt. These foreign debts become more difficult to service, reducing confidence among the people in their domestic currency.
To Reduce Sovereign Debt Burdens
A government may be incentivized to encourage a weak currency policy if it has a lot of government issued sovereign debt to service on a regular basis. If debt payments are fixed, a weaker currency makes these payments effectively less expensive over time.
Take for example a government who has to pay $1 million each month in interest payments on its outstanding debts. But if that same $1 million of notional payments becomes less valuable, it will be easier to cover that interest. In our example, if the domestic currency is devalued to half of its initial value, the $1 million debt payment will only be worth $500,000 now.
Again, this tactic should be used with caution. As most countries around the globe have some debt outstanding in one form or another, a race to the bottom currency war could be initiated. This tactic will also fail if the country in question holds a large amount of foreign bonds since it will make those interest payments relatively more costly. (See also: Why Your Pension Plan Has Sovereign Debt in it.)
The Bottom Line
Currency devaluations can be used by countries to achieve economic policy. Having a weaker currency relative to the rest of the world can help boost exports, shrink trade deficits and reduce the cost of interest payments on its outstanding government debts. There are, however, some negative effects of devaluations. They create uncertainty in global markets that can cause asset markets to fall or spur recessions. Countries might be tempted to enter a tit for tat currency war, devaluing their own currency back and forth in a race to the bottom. This can be a very dangerous and vicious cycle leading to much more harm than good.
本文翻译由兄弟财经提供
文章来源：http://www.investopedia.com/articles/investing/090215/3-reasons-why-countries-devalue-their-currency.asp