In this study, Gini coefficient index (GINI), Teil index (T), tenth to first deciles ratio (D10/D1), upper four deciles concentration ratio (UPCR4), in which the rich situation and lower four deciles (DOWNCR4) that indicate the poor situation has been used for evaluating income distribution.
The above mentioned indices calculated during the 3 periods of development programs (1969-1979) before revolution, the second one during 1979-1988 and the last one (i.e. 3 Development program) during 1989-2004.At the end, having reviewed various income distribution indices, we can conclude that most of the inequality indices had the upward trend during the years 1969-1982. At the same time, the mentioned indices had the downward trend during the years 1983-2004. The results show that the upper 10 percent of the rich has almost 27 times higher income share than the lower 10 percent of the poor during the year 1979. In addition, this ratio has decreased to 17% and 14%during the years 1989 and 2004, respectively.Also, having considered in GINI and Theil, it is concluded that income distribution policies had significant effect on decreasing the income inequality in Iran during the 3 development programs (i.e. 1989-2004).