Testing the Efficient Market Hypothesis in G8 Countries: New evidence from Unit Root Tests with Fourier Shifts

The aim of this study is to test the validity of the efficient market hypothesis for stock market indices in G-8 countries (USA, Germany, France, England, Italy, Japan, Canada, and Russia). The augmented Dickey-Fuller (ADF), residual augmented least squares (RALS)-ADF, Fourier-ADF, and Fourier-Kapetanios-Snell-Shin (Fourier-KSS) unit root tests are used to do this. The longest possible period was used as the analysis period by considering the data available for each index. Unlike the literature, the validity of the efficient market hypothesis for stock market indices in the G8 countries has been comprehensively and comparatively examined by simultaneously considering Fourier breaks, non-normal distribution, and non-linearity. According to the empirical findings, the null hypothesis was not be rejectable for all the unit root tests that were applied to the stock market indices from Germany, France, and Japan. In other words, strong evidence has been obtained for the validity of the efficient market hypothesis for the stock market indices from these three countries. On the other hand, the null hypothesis was rejected for Russia's stock market index as a result of the unit root tests applied apart from ADF, with the results that emerged indicating the efficient market hypothesis to be invalid for that case. Different results were observed to have been caused by taking into account Fourier breaks and nonlinearity in other indices. The Fourier-KSS test considers the nonlinearity in a dataset using Fourier breaks and was found to provide more evidence for the invalidity of the efficient market hypothesis compared to the other types of tests. This reveals the importance of choosing the appropriate test for the data.