Testing the Random Walk Hypothesis for Real Exchange Rates

Abstract

This chapter aims to analyze the efficiency, in its weak form, in the exchange rates of Brazil vs. USA, Australia, Canada, Europe (Euro Zone), Switzerland, United Kingdom, and Japan from July 1, 2019 to September 20, 2020. The results suggest that exchange rates show signs of (in)efficiency, in their weak form (i.e., the values of the variance ratios are lower than the unit), which implies that returns are autocorrelated over time, and there is reversal to the average. In corroboration, the results of detrended fluctuation analysis (DFA) show persistence in yields (i.e., the existence of long memories), thus validating the results of the Lo and Mackinlay model that show autocorrelation between the series of yields. As a conclusion, the authors show that the assumption of market efficiency may be questioned, since the forecast of market movement may be improved if the lagged movements of the other markets are taken into account, allowing the occurrence of arbitrage operations in these foreign exchange markets.