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lios consisting of stocks with a high price earnings ratio. Basu (1977) shows that investors holding low price earnings ratio portfolio earned higher returns.

The existence of market anomalies have important implications. If stock returns do not follow a random process, then it is possible to design profitable trading strategies based on historical information

2.6.1 Empirical Evidences from Developing Countries
Despite the large number of empirical studies that have been conducted to test the validity of the Efficient Market Hypothesis (EMH) in developed countries with booming financial markets, studies to support or dispute the efficiency or inefficiency of the African stock markets are quite limited. There is a small number of empirical studies analyzing emerging African equity markets with regards to weak form of market efficiency test. While some of these studies have analysed single markets ( e.g. Samuels and Yacout 1981; Parkinson 1984; Ayadi 1984; Dickinson and Muragu 1994; Osei 1998; Olowe 1999; Mecagni and Sourial 1999; Asal 2000; Adelegan, 2004; Dewotor and Gborglah, 2004; Ntim et al., 2007), others have analysed groups of countries (e.g. Claessens et al., 1995; Magnusson and Wydick, 2002; Smith et al., 2002; Appiah-Kusi and Menya, 2003; Simons and Laryea, 2004; Jefferis and Smith, 2005).

However, while there are only a few empirical studies, their conclusions as to the efficiency and predictability of future stock returns have been mixed. For example Dickinson and Muragu (1994) shows that the Kenyan stock market is weak form efficient, in contrast to the results of Parkinson (1984).

Also, most of the existing studies made use of conventional weak form testing techniques such as serial correlation tests. Samuels and Yacout (1981) and Parkinson (1984) were among the first to use serial correlation tests to examine the weak form efficiency on the African continent. Samuels and Yacout analysed the weak form market efficiency in weekly price series of 21 listed Nigerian firms from 1977 to 1979 and provided empirical evidence that the market was efficient. Parkinson on his part, analysed monthly price series of 30 listed Kenyan firms from 1974 to 1978 and rejected the weak form efficiency. Dickinson and Muragu (1994) reinvestigated the Kenyan market by applying run and serial correlation tests to weekly stock price series of 30 listed companies on the Nairobi Stock Exchange and their results were in contrast with Parkinson (1984). They demonstrated that successive price changes are independent of each other for the majority of the companies investigated.

Most of the developing countries suffer from the problem of thin trading (Mlambo and Biekpe, 2005). The problems caused by thin trading have been widely acknowledged in financial market researches (e.g., Dimson, 1979; Cohen et al. ,1983; Butler and Simonds, 1987; Lo and Mackinlay, 1990a and b; Bowie, 1994; Muthuswamy and Whaley, 1994) . Fisher (1966) who was the first to identify the bias caused by thin trading in the serial correlation of index returns, explained that recorded prices of securities are not necessarily equal to their underlying theoretical values. This is because when a share does not trade, the price recorded remains the closing price when the share was last traded.

However, while most of the African stock markets suffer from thin trading, many existing studies fail to