Stock Market Efficiency : A Test of the Swedish Stock Market in the Weak Form

Abstract: Background: A well-known study, similar to ours, was made in 1985 in America, showing that "loser" portfolios outperformed the market while "winner" portfolios earned less return than the market. This finding is not in accordance with the theory of efficient markets. If a market is efficient, there should be no possibility of making sustainable excess returns and prices should follow a random walk. Purpose: The purpose of this thesis is to study a "winner" portfolio and a "loser" portfolio in order to establish whether the Swedish stock market is efficient in the weak form. We will study the efficiency of the A-list at Stockholm Stock Exchange. Delimitations: We test efficiency of the Swedish stock market in the weak form. Our investigation comprises stocks registered on the A-list of the Stockholm Stock Exchange. We do not take tax- and transactions costs into consideration in this study. Methodology: "Winner" and "loser" portfolios are formed for the period 1997- 2002. We keep the portfolios during a test period of one year, i.e. form new portfolios at the end of each year. The first winner and loser portfolios are selected on the last day of trading in 1996 and the last two portfolios are selected on the last day of trading in 2001. Results: Our result indicates that the Swedish stock market is efficient in the weak form during the period 1997-2002.