||One of the most important characteristics of joint stock companies is separation of ownership from management. This fact along with the gradual influence of management in making changes in accounting procedures due to lack of coherent methods, also exclusive access of managers to a part of financial information, and characteristics of accrual accounting together with motivations such as bonus and lawbreaking induces the motivation in managers to exert various methods for their favorite interests make changes in the profit in contradiction with interests of other groups. income smoothing is a topic that provides this objective of management In this regard.
The objective of this study is to reveiew the factors affecting income smoothing among the companies accepted by Tehran Stock Exchange in an approach to determine the amount of influence of effective factors, as well as introducing a model for the purpose of prediction of income smoothing possibility. in this study relationship between income smoothing and such varibles profitability,company size and industry are tested based on three null hypotheses .The statistical population comprises all companies accepted in Tehran stock exchange for the period (1378-1382) and the statistical sample includes 155 companies (54% of the total population).
For the purpose of study, the sample companies classified into smoothers and non-smoothers groups based on eckel index and the effect of three independent variable were investigated. Then by considering the effectiveness of each factor, the amount of influence of effective factors and finally the accuracy rates of model’s prediction were studied.
Statistical methods comprises: descriptive statistics (means and frequency distribution) in order to establish an information bank of sample companies, uni-variate tests for the purpose of initial investigate hypotheses and logit multi-variate regression model in order to comprehensive investigate the hypotheses and analyze the relationship among variables.
The results of running uni-variable tests and logit analyzes indicate that the profitability variable influences the income smoothing and income smoothing is greater in less profitable companies. Also the effect of profitability variable on smoothing was studied and it was concluded that by a one-unit increase in the profitability of company, the probability of smoothing decreases by -1/31. finally, the results of model accuracy tests and estimated model coefficients showed that the model is acceptable to predict the probability of income smoothing by companies.