该理论指出，在一个较长的时间段内，任何两国之间的汇率应该朝着某一方向移动，从而使得在两国购买等量的货物和服务的价格相等。

This says that, in the long run, exchange rates should move toward rates that would equalise the prices of an identical basket of goods and services in any two countries.

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比如，这是在购买货物和服务的过程中最常见沟通方式。

For example, this is the most common form of communication in the process of purchasing goods and services.

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现场购买是当他们需要时的采购货物和服务，通常是在当前的市场价格。

Spot buying is the purchase of goods and services as they are needed, usually at prevailing market prices.

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