Investigation of market Efficiency: An event study of Insider Trading in the Stock Exchange of India

Abstract

That company insiders earn profits from stock trading does not surprise most financial economists, but that outsiders can earn abnormal returns by using publicly available insider trading data constitutes a serious exception to stock market efficiency. The semi-strong form of the efficient market hypothesis assumes all available public information is fully reflected in a security's market price. The exponential growth of the Indian stock market provides a huge potential for its achievement of the pricing efficiency at a higher level. The present study aims to examine whether the Indian stock market is pricing efficient in its semi-strong form. Such examination was made in the context of the price reaction to the insider trading witnessed by 17 constituent stocks of CNX Nifty during the period from January 2000 to December 2007 by application of the market model of the event study methodology. Although no statistically significant abnormal return was found to be generated on and around the event day, the cumulative average abnormal returns for most of the time intervals in the pre- and post-announcement periods were statistically significant. However, it was observed that the cumulative average abnormal returns for the shorter time intervals around the insider trading day were statistically insignificant. Thus the study failed to provide any strong and consistent evidence in support of the strong form of pricing efficiency of the Indian stock market..