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Private sector investment is fundamental in economic development. Here, we are trying to show which factor is more important. This study was written with focus on the theories of investment and investment process in Iran. A lot of work has done in this area in Iran, but they did not pay attention much to the non-economic factor which affects on investment. We have analyzed the theories that define influence of qualitative variables on investment. These variables cause uncertainty for economy, so we studied the impact of them with attention to a specific situation. In the last chapter we used qualitative variables in an econometric model. Our concern was finding the reasons of existence of these types of variables. And then we focused on them. At the end of our paper we have suggested some policy implication.
JEL classification: R42, D8