Using Duncan & Etebari's (1990) method, an initial sample of five securities firms in the KLSE which posted the largest price gains for each of the 49 trading weeks of 2005 will be obtained, all of which were queried by the KLSE during the same period as well. From the price data, initial raw returns will be calculated which in turn will be used to estimate average and cumulative average returns. Conversely, a measure of 'unusual' trading volume will be obtained from the samples by still using Duncan & Etebari's method in measuring abnormal trading volume. A t-test will be applied to determine if behaviour of the average and cumulative returns and positive abnormal volume results are significantly different from zero.
Information disclosure is one of the most crucial ingredients for the effective operation of stock markets. Yang and Wu (2002) cite that the financial crisis in Southeast Asian countries that broke out in 1997 and the Enron bankruptcy case in the United States capital market in 2001 provide negative examples that teach about the importance of information on the stock market. Inadequate and even fraudulent information disclosure would bring tremendous negative effect on the effective operation of the whole capital market (Yang and Wu, 2002).
As a listed company making full disclosure reduces information asymmetry and enables the public to have information necessary to make informed decisions (Hwa, 2004), Bursa Malaysia demands and requires issuing listed company for explanation when it observes unusual share price or trading volume changes for that company. As stated in the Bursa Malaysia Listing Requirements, paragraph 9.02(2), "a listed company is required to make immediate public disclosure of any material information." When information is voluntarily withheld, the company must closely monitor the share price of the company during the period. A company must make immediate announcement to Bursa Malaysia upon detecting unusual circumstances such as heavy share transaction volume, unusual market activity, surfacing rumours or news and signs that insider trading are happening. The company under these situations must immediately publicly clarify, confirm or deny the rumour or report (Hwa, 2004). Such a response may have information content and thus market impact.
The role of informational content of companies' responses to unusual market activity observed by the Kuala Lumpur Stock Exchange is the prime component of the study. The theory of efficient capital markets provides that stock prices will respond to announcements only when the information being announced is new and unexpected. Because changes in stock prices are unpredictable, when information is announced that has been expected by the market, the stock price will remain unchanged (Mishkin, 2003). Studies done by Teitenberg and Wheeler (2001) on information disclosure strategies write that public announcements do seen to affect the market valuations of firms.
Effective information disclosure also entails the reduction or the control of insider trading in the stock market. In