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Changes infertility ratesasone of the factors affecting the demographic changes and its rolein the labor supply and there fore economic growth, as an important element ofsocio-economic development of every country is considered. So that the importance of demographic changes in each country in recent years has increased resulting aging population in general and specifically decreased fertility that increased concerns for the global economy and the majority of developing countries-including Iran. However, the range of empirical studies in incurred countries is very limited and in most studies, the surface shape of the subject has investigated in a simple line a reconometric model. Thus this study investigates the impact of fertility’s changes one conomic well-being in selected MENAcountries over the 1970-2010. We apply dynamic consumer optimization model that incorporates end ogenous fertility as well as end ogenous education and health investments offered by Prettner and et al. (2013). The estimation results of non-linear panel smooth transition regression model reports the negative effect of fertility and positive effect of revenue and population on effective labor force, which show that the quantity-quality trade off in population acts in favor of labor force and increases its quality and causes output growth and well-being. This issue is in ferable from positive effect of population on education and health-as delineator indices for well-being- in the countries under investigation.