In the field of international economics and finance, the concept of Purchasing Power Parity (PPP) has been among the most enduring. Absolute PPP (which is in its ultimate form) indicates that on condition that a common currency dominates prices, people could purchase the same commodity anywhere for the same price. The law of one price provides certain theoretical guidance for the concept, assuming that arbitrage in many types of commodities equalizes prices. After the gold standard collapse during World War I, Cassel (1922) suggested that relative gold parities could be restored by using PPP. He said that post-war exchange rates were set by countries in terms of PPP by making sure that the change in their post-war and pre-war exchange rates was equal to the difference between their post-war and pre-war inflation rates. Since then, PPP has been used by economists to set and predict exchange rates, in adjusting cross-country incomes to explain differences in prices, and as a foundation of models in international macroeconomics.
Purchasing Power Parity was firstly proposed as a short-run equilibrium by large numbers of international economists in the first few years after the collapse of the Bretton Woods system in the early 1970s. It was then attacked from both theoretical and empirical aspects during the late 1970s through the mid-1990s. As a result, over the last three decades, a large literature has built up that examines the deviation between data and theory, and the research achievements have offered a more profound understanding of the application of PPP in both the short run and the long run. Since the mid-1990s, larger datasets and nonlinear econometric methods have specially met the need of improving forecast accuracy: The gap narrowed between theory and data with the narrowed deviations between real exchange rates and PPP, and some degree of confidence in long-run PPP began to emerge again. The idea of long-run PPP now getting perhaps its most powerful support in more than thirty years shows a radical reversion in economic thought in this regard.
在国际经济和金融领域的概念，购买力平价（PPP）一直是最持久的。绝对购买力平价（这是它的最终形式）表明，条件是共同的货币主导价格，人们可以购买同一商品的价格一样的地方。一价定律的概念提供了一定的理论指导，假设在许多类型的商品套利均衡价格。第一次世界大战期间，金本位制崩溃后，卡塞尔（1922）表明，可以通过使用相对黄金平价PPP恢复。他说，战后汇率设置从PPP国家确保他们在战前战后和汇率变化相当于战前战后与通货膨胀率之间的差异。自那时以来，PPP是经济学家所使用的集和预测汇率的调整，在越野收入来解释不同的价格，并在国际宏观经济学模型奠定了基础。
购买力平价是首先提出的一种短期均衡在最初几年的国际经济学家大量在1970年代初布雷顿森林体系崩溃后。然后攻击从理论和实证两个方面在20世纪70年代末到90年代中期。因此，在过去的三年，一个大的文献建立了检验数据和理论之间的偏差，其研究成果提出了PPP在短期和长期的应用有一个更深刻的了解。自上世纪90年代中期以来，更大的数据集和非线性计量经济方法有专门接见了提高预测精度的需要：差距的缩小理论与数据之间的偏差与缩小实际汇率和购买力平价之间，和一定程度的信心开始出现了长期的PPP。长期的PPP的想法，现在也许是其最有力的支持，在三十年多的显示在这方面的经济思想激进的逆转。
