Therefore, if currencies are determined by the relative prices of tradables, but PPP is calculated from a basket that includes non-tradables, such as the Big Mac, the currencies of poor countries will always look undervalued.

• 因此，如果货币是由可贸易货物与服务的相对价格来决定的，但是由于购买力平价是根据单位不可贸易货物，如巨无霸来计算的，穷国的货币显得总是被低估了。