Abstract
Section 44 of the Constitution of Islamic Republic if Iran emphasizes the prevention on Monopoly through appropriate regulation and legislation.
In this study we measure the concentration ratio in the selected industries (Petrochemical، Automobiles، Iron، Glass and Sugar) for the period of 1998-2006. The result show a high degree of concentration which may decline over time as the number of producers increase without ay significant change in the basis of monopoly power.
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