Efficient Security exchange may leads to allocating optimum resources. Efficient market is a market which prices amend and adjuste in it immediately based on the new information. Many researches has been performed to show the relationship between prices variation and new information in an efficient market.
In this study we have considered the effect of the news about stock split and stock dividend, on stock price in order to determine its efficieney in Tehran security exchange.
All authorities belive such news have not really worth to a firm theoretically. In the other word, such news don’t create abnormal return, so here it has been supposed hypothetically that:
»The average of the abnormal sample return in the meetings date equal zero.«
This study contains two periods from 1372 to 1380 which has been considered separately, and its methodology has been taker exactly from (Gentelmans) F.F.J.R who have studied the efficiency of New — York security exchange in semi strong form.
The results show the abnormality return in meetings, so the hypothesis of the research and semi strong form of the efficient market of Iran security exchange, is rejected.