中國和美國哪個國家的經濟規模更大

 

美國的經濟規模在1982年超過英國後一直處於世界第一的位置，但是他的王朝可能就要結束了。根據一項跨國GDP對比，中國現在是世界上最大的制造商。但是，另一種方式的比較，美國的經濟規模還遠遠大於中國。比較哪個經濟體規模更大的最好的方法完全取決於一個人選擇的方法和比較的動機。

 

跨國比較的問題

GDP測量在給定時間内一個國家產生的產品和服務的貨幣價值。這裡的關鍵詞是貨幣，其價值本身是不可見的。人們只能觀察產品和服務交易時的價格。

 

在試圖比較以美元計價的美國商品和服務和以人民幣計價的中國商品和服務時變得很明顯，這是兩種不同單位的測量價值。除非人們了解兩種貨幣的轉換因子，不然兩種貨幣的比較是毫無意義的。幸運的是，我們確實有轉換因子，不幸的是，我們事實上擁有的兩個轉換因子存在巨大分歧。

 

這兩個轉換因子是市場匯率和購買力平價率（PPP）。根據世界銀行的數據，2014年中國以市場匯率測定的GDP為10.36萬億美元，而美國為17.42萬億美元。然而，世界銀行根據購買力平價測定中國GDP為18.03萬億美元，美國仍然是17.42萬億美元。這其中存在很大差距。

 

市場匯率和購買力平價對比

市場匯率是使用時間段最後的市場外匯率或者該時間段平均匯率。而購買力平價匯率相反，使用把一種貨幣購買和使用另一種貨幣購買相同數量的產品和服務的轉換率。

 

雖然市場匯率看起來非常簡單，但是我們來看一個例子更好的解釋購買力平價測量。假設在美國買一個漢堡要平均花費5美元，在中國則花費17元人民幣。這意味著美元和人民幣的購買力平價轉換率為17/5=3.4，因為這將有效的使漢堡在兩國的價格相同。

 

然而，跨國GDP比較根據單一產品的價格是遠遠不夠的。需要考慮大量的產品和服務，這也是國際對比項目（ICP）嘗試做的事情。ICP發展了一個包含超過1000種商品和服務的全球核心列表。

 

優點和缺點

PPP變成一種重要方式的原因之一是市場匯率方式把GDP轉換到同一種貨幣，而忽視了不同國家貨幣的相對購買能力。雖然市場匯率方式計算國際間商品和服務的購買能力，它忽視了許多商品在一個國家比另一個國國家便宜很多的事實，這在像中國這樣的發展中國家尤為真實。

 

PPP的另一個優點是相對穩定，而市場匯率波動比較大。即使真實增長率比較穩定，測量的增長也會隨著市場匯率波動。

 

市場匯率的缺點在闡述PPP優點的時候我們已經說明。然而，市場匯率的一個優點是比PPP容易計算。

 

總結

在試圖確定哪一種GDP測量方式在比較國家的經濟規模最好時，重要的是要明白你為什麼要做比較。如果你的目標是測量生活水平，那就使用PPP。如果你對地緣政治更關心，那麼市場匯率就會更適合你。以中國和美國哪個國家的經濟規模更大是個好標題，但是如果你不知道GDP測量要做什麼則它根本無關緊要。

 

Which Economy Is Larger - The United States or China? 

 

By Matthew Johnston | October 12, 2015 

| 

The U.S. economy has been the world’s largest since overtaking the U.K. economy in 1872, but its reign may just be over. According to one method of making inter-country GDP comparisons, China is now the world’s biggest producer. (See related: The 3 Industries Driving China's Economy.) Yet, according to another method, the U.S. economy is still significantly larger than China’s. The best method, and hence which economy is larger, all depends on one’s methodology and motivations for making the comparison in the first place.

 

Inter-Country Comparison Problems

 

The GDP measures the monetary value of all final goods and services produced in a country over a given period of time. The key word here is monetary, since value itself is unobservable. All one can observe are the prices (i.e. monetized values) at which goods and services exchange. So far so good.

 

Problems soon become evident when trying to compare U.S. goods and services priced in dollars with Chinese goods and services priced in yuan, which are two different units to measure value. Unless one knows the conversion factor, comparisons between two separate currency units are meaningless. Fortunately, we do have a conversion factor; somewhat unfortunately, we actually have two conversion factors that can have large discrepancies.

 

The two conversion factors at our disposal are market exchange rates and purchasing power parity (PPP) rates. According to the World Bank, at market exchange rates, China’s GDP for 2014 was $10.36 trillion, compared to the U.S. figure of $17.42 trillion. However, the World Bank’s figures at PPP rates reveal that China’s GDP for 2014 was $18.03 trillion, while the U.S. figure is still the same $17.42 trillion. That’s a significant difference.

 

Market Exchange Rates vs. Purchasing Power Parity

 

The market exchange rate measure uses the prevailing rate in the foreign exchange market either at the end of the period in question, or averaged over that period. The PPP exchange rate measure, contrastingly, uses the rate at which one currency would need to be converted to another currency in order to buy an equivalent amount of goods and services in each country.

 

While the market exchange rate measure seems simple enough, let’s look at an example to better illustrate the PPP measure. Suppose that it costs an average of $5 to buy a hamburger in the U.S., while it costs an average of 17 yuan to buy one in China. That means the PPP exchange rate of dollars to yuan should be 17/5 = 3.4, since that would be the rate that would effectively make hamburgers the same price in each country.

 

However, basing inter-country GDP comparisons on the relative prices of a single good in separate countries is inadequate. It is important to consider a broad range of goods and services, which is exactly what the International Comparisons Program (ICP) attempts to do. The ICP has developed a Global Core List of over 1,000 goods and services comparable across different regions and priced by all participating countries.

 

Advantages and Disadvantages

 

One of the reasons that PPP became an important method was that where the market exchange rate method converts GDP to a common currency, it fails to take into account the relative purchasing power of each currency in its respective country. While the market exchange rate method accounts for the purchasing power of internationally traded goods and services, it fails to reflect the fact that many goods and services are relatively cheaper in some countries than others; this is particularly true of developing countries like China.

 

Another advantage of PPP rates is that they tend to be more stable over time, whereas market exchange rates are much more volatile. Aggregate measures of growth will fluctuate with the same volatility as exchange rates even when actual growth rates are relatively stable.

 

The disadvantages of the market exchange rate method have been noted already by highlighting the relative advantages of the PPP method. However, one advantage of market exchange rates over PPP rates is the relative ease with which one can do the calculations. Because there is so much more involved in the PPP calculations (i.e. choosing the appropriate basket of goods and services and assigning appropriate weights to each), it is much easier for inaccuracies to be introduced.

 

The Bottom Line

 

In trying to determine which GDP measurement method is best for comparing the relative size of different economies, it is important to understand why you are making the comparison in the first place. If your goal is to use GDP as a measure to compare living standards, then using the PPP method may be your best option as it more adequately measures the relative purchasing power of each currency within its respective country. However, if your concerns are geopolitical, then the exchange rate method is best as it is better at measuring the relative importance of a country’s trading partners. The question of whether the Chinese economy is bigger than the U.S. economy may make nice headlines, but it matters little if one is unsure of why GDP measurements matter to begin with. (See also: China's Economy: Transition to Sustainable Growth.)

 

本文翻譯由兄弟財經提供

文章來源：http://www.investopedia.com/articles/investing/101215/which-economy-larger-united-states-or-china.asp