A Comparative Analysis of Weak and Semi-Strong Form Efficiency of Nigerian and South African Foreign Exchange Market

Foreign exchange market is said to be efficient if all available information are reflected in its exchange rates. An efficient foreign exchange translates to absence of profitable and exploitable trends which means that it is impossible for market participants or private agents to outperform the market. This study investigated the weak and semi-strong form efficiency of Nigerian and South African foreign exchange market to determine the significance of past exchange rates in predicting the present rate which is the test of weak form efficiency and it examined the co-integration relationships between selected pairs of exchange rate to determine the semi-strong efficiency. The secondary data used in this study were sourced mainly from the Central Bank of Nigeria Statistical Bulletin, the South African Reserve Bank Bulletin and the oanda exchange rate websites. The data used were the inter-bank spot exchange rates of Naira and Rand to Swiss Franc, Euro, Pounds, Dollar and Yen for the period of January 2010 to December 2017. The Augmented Dickey Fuller (ADF) test and the Phillip Peron (PP) test were employed to determine the weak form efficiency while the Variance Decomposition, Granger Causality and Co-integration tests were used to determine the semi-strong form efficiency of both countries. The results of the study revealed that the Nigerian foreign exchange market is efficient in the weak and semi-strong form at 5% level of significance while the weak form efficiency of South African foreign exchange market revealed mixed results. The market is efficient in the weak form except for the case of Rand to Dollar and Rand to Yen which showed inefficiency. The market is equally efficient in semi-strong form. The study concluded that market participants cannot make exploitable profits by trading in both markets because all past and publicly available information are already incorporated in the prices of exchange rates. It was therefore recommended that the inter-bank market in both countries should be well monitored and managed by the regulatory authorities so as to promote the effective and efficient smooth functioning of the foreign exchange market as well as achieving a stable and realistic exchange rates.

Weak Form Efficiency Evaluation at the Bulgarian Stock Exchange Using Runs Test

The article aims to test the weak form of efficiency of a sample of public companies on the Bulgarian Stock Exchange (BSE) for the period from October 2000 to June 2020 on the basis of weekly returns. 9 companies and the SOFIX index meet the set criteria for inclusion in the sample. Descriptive characteristics of the weekly returns, autocorrelations and the extended Dickie and Fuller (ADF) stationary test are presented. The methodology of the Runs Test is considered. The Runs Test results reject the weak form of efficiency for the SOFIX index and some of the companies. Autocorrelations of returns further support the rejection of the weak form of efficiency.

Weak form market efficiency: A case study of Asia-Pacific markets

This study aims to test the weak form market efficiency for five developed markets, nine emerging markets and three frontier markets in the Asia-Pacific region. The tools applied in the test of this form of market efficiency are serial correlation test, runs test and unit root test. The analysis is performed by using logarithm return for the period of 2008 to 2018. For all markets in our research, the results strongly reject the weak form efficiency when the unit root tests are carried out, while the results from the Durbin-Watson test are in complete contrast. However, in the runs test and variance ratio test, the results provide mixed evidences of weak form efficiency of the markets

Are African Stock Markets Inefficient or Adaptive? Empirical Literature

This chapter reviews empirical studies on weak form of efficiency with the aim of establishing whether the African market is inefficient or adaptive. The reviewed studies are categorised based on their methodological approaches to compare the power of linear and non-linear models in testing for weak-form efficiency. The studies on calendar anomalies, an indication of weak-form inefficiency, are reviewed to assess whether these anomalies are adaptive as portrayed by the relatively recent theory of adaptive market hypothesis (AMH). The scope of reviewed studies is also extended to developed and emerging markets to gain a broad comparison of the findings. This review revealed that non-linear dependence has been revealed in stock returns suggesting that non-linear models are best fit to test for the stock market efficiency. Reviewed studies produced contradictory findings with some supporting and others rejecting weak-form efficiency. Thus, most studies support the AMH, which suggests that market efficiencies and anomalies are time changing. This chapter concludes that most of the existing studies on AMH have been carried out in markets other than Africa, and hence, further empirical studies on the evolving and changing nature of efficiency in African stock markets are recommended.

Further evidence on efficiency of Bahrain Bourse: A high challenge for other industries

The purpose of the present study is to provide further evidence of the weak form efficiency of the Bahrain Bourse. The research methodology is based on daily closing index values of the Bahrain Bourse from 2011 to 2015 in order to test the efficiency of the stock market while runs test, Autocorrelation Function, and advance tools such as ARCH and GARCH models and Hurst Index to provide further evidence of the weak form efficiency of the Bahrain stock market. For instance, a volatile and inefficient stock market has a negative impact on textile and apparel industry in the Kingdom of Bahrain, which is one of the most prosperous and attractive industries in the country. The empirical results revealed that Bahrain stock market does not follow normal distribution and the successive price changes are not independent. Further, ARCH effect is significant and indicative of a time-varying conditional volatility. There is an arbitrage opportunity and extreme mispricing in the Bahrain stock market as indicated by the GARCH (1,1) model. The results of the Hurst exponent also confirm the inefficiency of the market. The results of these tests are consistent indicating that the Bahrain stock market is inefficient

How to compare market efficiency? The Sharpe ratio based on the ARMA-GARCH forecast

This paper derives a new method for comparing the weak-form efficiency of markets. The author derives the formula of the Sharpe ratio from the ARMA-GARCH model and finds that the Sharpe ratio just depends on the coefficients of the AR and MA terms and is not affected by the GARCH process. For empirical purposes, the Sharpe ratio can be formulated with a monotonic increasing function of R-squared if the sample size is large enough. One can utilize the Sharpe ratio to compare weak-form efficiency among different markets. The results of stochastic simulation demonstrate the validity of the proposed method. The author also constructs empirical AR-GARCH models and computes the Sharpe ratio for S&P 500 Index and the SSE Composite Index.