Since Cassel (1922) proposed the theory of Purchasing Power Parity, only after 60 years until the 20th century, the rigorous empirical evidence appeared to prove that PPP holds over a long period of time (Friedman and Schwartz, 1963, Gaillot, 1970). Balassa (1964) and Samuelson (1964) proposed theory of productivity bias hypothesis provides support to the PPP too, and it had a tremendous impact. During the next 30 years, PPP was one of the most discussed topics in economics but the results of these discussions varied greatly. This result not only led to the renewal and progress of the quantitative methods used to test the purchasing power parity condition, but also promoted the growing purchasing power parity theory. Before the 1970s, the empirical studies of PPP used the simple OLS regression only. In the 1980s, the mainstream empirical research methods included the two-phase EG method, the ADF test, variance ratio, Fractional Integration approach, etc. After a detailed study on the bilateral floating exchange rate data using the data from industrialized countries after 1973, economists such as Dardy (1983), Frankel (1986), Meese and Rogoff (1988) arrived at a basic conclusion: the exchange rate is a random walk process, and the purchasing power parity does not hold.
After Engel and Granger (1987) proposed two-step cointegration test theory, a large number of empirical tests were put forward to testify the long term PPP condition. Taylor (1988) enlarged the constraints and tested whether there was a cointegration relationship between the nominal exchange rate and the relative price.
由于卡塞尔（1922）提出的理论，购买力平价，仅在60年后，直到20世纪，严格的实证证据似乎证明PPP持有过了很长一段时间（弗里德曼和施瓦茨，1963年，盖洛特，1970）。巴拉萨（1964）和萨缪尔森（1964）提出的理论的生产力偏置假说提供了支持PPP，并产生了巨大的影响。在未来30年，PPP是经济学中讨论最多的话题之一，但这些讨论的结果差异很大。这一结果不仅导致用来测试购买力平价条件的定量方法的更新和进步，也促进了日益增强的购买力平价理论。在20世纪70年代之前，使用的购买力平价的简单OLS回归的实证研究。在20世纪80年代，主流的实证研究方法就双边浮动汇率数据使用的数据来自工业化国家在1973年后经过了详细的研究，包括两相EG方法，ADF检验，方差比，分数次积分方法等经济学家如Dardy（1983），弗兰克尔（1986），米斯和Rogoff（1988）到达一个基本结论：汇率是一个随机游走过程，购买力平价不成立。
恩格尔和Granger（1987）提出了两步协整检验理论后，大量的实证检验，提出了作证的长期购买力平价条件。泰勒（1988）扩大测试的约束和名义汇率的相对价格之间是否存在协整关系。
