《經濟學人》精選:爲什麼說中國的漢堡還不夠貴?

Big Mac index
Bun fight
Why China needs more expensive burgers
Oct 15th 2010

A WEAK currency, despite its appeal to exporters and politicians, is no free lunch. But it can provide a cheap one. In China a McDonald's Big Mac costs just 14.5 yuan on average in Beijing and Shenzhen, the equivalent of $2.18 at market exchange rates. In America the same burger averages $3.71. That makes China's yuan one of the most undervalued currencies in our Big Mac index, which is based on the idea of purchasing-power parity. This says that a currency's price should reflect the amount of goods and services it can buy. Since 14.5 yuan can buy as much burger as $3.71, a yuan should be worth $0.26 on the foreign-exchange market. At just $0.15, it is undervalued by about 40%. The tensions caused by currency misalignments prompted Brazil's finance minister to complain last month that his country was a potential casualty of a “currency war”. The Swiss, who avoid most wars, are in the thick of this one. Their franc is the most expensive currency on our list.

參考譯文：
儘管弱勢貨幣對於出口商和政府來說是好事，但這並不是免費的午餐。不過倒是可以提供一份便宜的午餐。在中國，一個麥當勞巨無霸在北京和深圳的平均價格爲14.5元人民幣，按市場匯率相當於2.18美元。在美國，同樣的漢堡平均售價是3.71美元。按照以購買力平價指標爲基礎的巨無霸指數來看，人民幣被低估了不少。根據巨無霸指數理論，貨幣的價格應該反映其可以購買的商品和服務的數量。既然14.5元人民幣可以購買相當於美國3.71美元的漢堡，1元人民幣應該在外匯市場上等值於0.26美元。但實際僅爲0.15美元，即人民幣被低估了大約40%。由於貨幣失調導致的緊張氣氛，使得巴西財長上個月抱怨說，該國成爲了“貨幣戰爭”的潛在受害者。瑞士雖然（作爲中立國）避開了大部分戰爭，卻避不開這場貨幣戰爭。瑞士法郎在我們這張列表中是被高估得最多的貨幣。小編選注：
The Big Mac Index is published by The Economist as an informal way of measuring the purchasing power parity (PPP) between two currencies and provides a test of the extent to which market exchange rates result in goods costing the same in different countries. It "seeks to make exchange-rate theory a bit more digestible".
The Big Mac PPP exchange rate between two countries is obtained by dividingthe price of a Big Mac in one country (in its currency) by the price of a Big Mac in another country (in its currency). This value is then compared with the actual exchange rate; if it is lower, then the first currency is under-valued (according to PPP theory) compared with the second, and conversely, if it is higher, then the first currency is over-valued.
兩國的“巨無霸指數”計算法，是以一個國家的巨無霸以當地貨幣的價格，除以另一個國家的巨無霸以當地貨幣的價格。該商數用來跟實際的匯率比較；要是商數比匯率爲低，就表示第一國貨幣的匯價被低估了（根據購買力平價理論）；相反，要是商數比匯率爲高，則第一國貨幣的匯價被高估了。
舉例而言，假設一個巨無霸在美國的售價爲$2.50，在英國的售價爲 £2.00；購買力平價匯率就是2.50 ÷2.00 = 1.25。如果當時匯率爲£1 = $1.82，則表示以兩國巨無霸的售價而言，英鎊兌美元的匯價被高估了45.6%（(1.82-1.25)÷1.25×%）。
批評者認爲，巨無霸漢堡包指數忽略了不同國家的稅收、利潤水平和原材料價格等因素的影響。

Purchasing power parity (PPP) is a theory of long-term equilibriumexchange rates based on relative price levels of two countries. The idea originated with the School of Salamanca in the 16th century and was developed in its modern form by Gustav Cassel in 1918. The concept is founded on the law of one price; the idea that in absence of transaction costs, identical goods will have the same price in different markets.
購買力平價（Purchasing Power Parity，簡稱PPP），又稱相對購買力指標，是一種根據各國不同的價格水平計算出來的貨幣之間的等值係數，使我們能夠在經濟學上對各國的國內生產總值進行合理比較，這種理論匯率與實際匯率可能有很大的差距。
該理論指出，在對外貿易平衡的情況下，兩國之間的匯率將會趨向於靠攏購買力平價。一般來講，這個指標要根據相對於經濟的重要性考察許多貨物價格才能得出。