Real income differences among human societies has been increasing in the past two centuries, and it is expected that these differences will not improve in the near future. Fundamental causes determing the reel income sources are combined into four
categories: luck, geography, culture and institutions. Reel income differences emerge because fundamental causes effect reel income sources. Conventional-mainstream economics alleges that developping countries should concentrate on these fundemantal causes and aim to adopt the culture and institutions of the developped countries. In this article, we examine the growth differences between Islamic countries and high-income OECD countries by employing statistical technigues and literature review. We conclude that if developping countries adopt the growth policies of conventional-mainstream economics, it will mean a process of westernization.