1, law of one price. Law of one price means that if calculated according to a currency, the price of the same commodity in different countries is usually the same. For example, the price of a loaf of bread in Switzerland is 1. 30 Swiss francs, then its price in the United States should also be 1. Thirty Swiss francs.

2. Big Mac index. From 65438 to 0986, The Economist replaced the purchasing power parity-Big Mac Index with a simple tool. The Economist named the study of this index "Hamburg Economy", and then other substitutes of purchasing power parity appeared, such as Coca-Cola index and Starbucks index of medium cup fresh milk coffee. The Big Mac index is still the most popular.