There are important uses of the centre/periphery dichotomy in sociology. Edwards Shils argues that the core of the society is a central value system which has a sacred character and is the ultimate source of authority, legitimizing the distribution of wealth, rewards and roles in the social system while the various social elites are fundamentally involved in the centre, other social groups are locked at the periphery. As the means of communication improve the centre becomes more extensive within society and previously periphery groups become increasingly involved in the centre value system and subject to its authority. In the development theory of Marxist sociologists like A.G Frank the centre refers to loci of the economic power in the global organization of production and distribution. In this perspective the global economy is conceived in terms of hierarchy of economic centers which through military, political and trade arrangement extract economic surplus from subordinate peripheral economies and regions. The distinction between the industrialized core and the under developed periphery is thus part of a more general theory of imperialism. The backwardness of peripheral economies is held to be a consequence of their dependence on various core economies and not the effect of their dependence on various core economies and not the effect of their poor resources, illiteracy, traditionalism or political instability.