A comparison between the developed and the developing countries reveals that the role of high and low birth rates in the level of development is a distinctive factor. The percent of children group in developing countries is nearly more than two times that of the developed countries. Since the children group is a cost bearer and inactive in economic aspect, therefore it wastes a lot of national income and retards the general development in the developing countries. In Iran the additional percent of children group spends more than 51 trilion tomans in each period. If these additional children were not born, we could save thd same money for construction of 3.5 million flats or train 5 million skilled persons. In that case we could obtain a five-fold per capita income annually and reach to an acceptable level of development.