2012年ACCA考试《F9财务报告》讲义辅导26

2012年ACCA考试《F9财务报告》讲义辅导26
Forms of efficiency
　　In order to decide whether a capital market exhibits pricing efficiency, research must be undertaken into security price movements and whether it is possible to make abnormal gains by acting on different kinds of information. Most of this research has been based on ordinary share price movements and three forms of efficiency can be described.
　　Weak form efficiency refers to a market where share prices fully and fairly reflect all past information. In such a market, it is not possible to make abnormal gains by studying past share price movements. Research has shown that capital markets are weak form efficient and that share prices appear to follow a ‘random walk’, the random changes in share prices resulting from the unpredictable arrival of favourable and unfavourable information on the market.
　　Semi-strong form efficiency refers to a market where share prices fully and fairly reflect all publicly available information in addition to all past information. In such a market it is not possible to make abnormal gains by studying publicly available information such as the financial press, company financial statements and records of past share price movements. Research has shown that well-developed capital markets such as the London Stock Exchange and the New York Stock Exchange are semi-strong form efficient.
　　Strong form efficiency refers to a market where share prices fully and fairly reflect not only all publicly available information and all past information, but also all private information (insider information) as well. In such a market, it is not possible to make abnormal gains by studying any kind of information. Since it is always possible to make abnormal gains by using insider information (even if governments have made this illegal), even well-developed capital markets cannot be described as strong form efficient. However, investors and analysts are often accurate in their estimates of what is happening inside companies and financial management theory considers well-developed capital markets to be highly efficient.