The Study of Relationship between Changes in Sale Market Share and its Effects on Return on Equity and Future Growth Opportunities in the Listed Companies of Tehran Stock ExchangeAhmad Ahmadpour First Author

In competition environment, the perpetuity of economic life entails of effort for acquiring greater share of market that is not ineffective of increasing in firms earning and changes in return on equity. In most researches, the sale of firm in comparison with other competitors is considered as the main factor to determine the market share and achieving more share of sale market in comparison with scope of competitor’s sale is entailed to use the prevalent strategies. In these research effects of change in firm's market share on return on equity is studied considering the price and momentum factors between 2004 to 2008 for 87 accepted firms in Tehran stock exchange. The result show that the current and future return on equity is affected by change in market share, but nevertheless of remain of that relation in 3 years, research variables has not enough predictability and with pass of time (more 2 financial periods) current performance has small effect in future performance that communicative of swings in capital market and sudden change in market share. Research show that valuation of current earnings with market share changes in regression model based on abnormal excess return, and based on regression model based on price that relation in conformed, but the stock price effects has trusty result that show effecting market share on price.