Core, Peripheral, Semiperipheral as Relational Concepts in World Systems Theory
"As regional world-systems became spatially larger and the polities within them grew and became more internally hierarchical, interpolity relations also became more hierarchical because new means of extracting resources from distant peoples were invented. Thus did core/periphery hierarchies emerge."
- Christopher Chase-Dunn 
"Wallerstein's world-system divides the nations and areas of the world into three units, designated core, peripheral, and semiperipheral (in the past some areas remained external to the system). These normative units are systemic and relational within the capitalist world economy. All parts of the system are dependent upon and interact with each other; any change in the system will impact upon the system as a whole.
Core nations dominate the economic structure of their historical time and strive to maintain or expand this authority. One fundamental element of a core nation is the ability to produce and distribute products. Another characteristic is a strong state machinery linked to a unified national culture. The state supports economic influence wielded by private businesspeople, merchants, and financial institutions, which play a vital role in core nations. Culture often serves as an ideological justification for dominance. The state also provides military force to protect and expand economic interests. Contemporary core nations dominate high technology, financial institutions, and high-profit industries. Within the context of the world-system, core nations compete among themselves for economic advantage.
Peripheral areas or nations (often colonies from the sixteenth to the twentieth centuries and defined as underdeveloped or semideveloped for a brief time in the twentieth century) serve the interests of the core nations. Peripheral areas provide agricultural products, luxury goods, raw materials, and cheap sources of labor. At times peripheral areas gained prominence, serving as key geographically located posts to protect trade routes between the core and the periphery. Peripheral areas are dependent upon core nations and have often been a source of conflict between core nations. Core methods of domination range from various forms of colonialism to anticolonial imperialism and economic dependency.
Last in the tripartite world-system are semiperipheral nations and areas. These serve as intermediate trading areas between the core nations and the peripheral areas. They also have small manufacturing sectors, geared to either local or international trade, and some capital accumulation.
Historically, some areas remained external to the world-system either by choice or neglect. By the twentieth century virtually every region on the globe had been consolidated into the modern capitalist world-system."
"Semiperipherality is the position of some of the polities in a core/periphery hierarchy. Some of the polities that are located in semiperipheral positions became the agents that formed larger chiefdoms, states and empires by means of conquest (semiperipheral marcher polities), and some specialized trading states in between the tributary empires promoted production for exchange in the regions in which they operated. So both the spatial and demographic scale of political organization and the spatial scale of trade networks were expanded by semiperipheral polities, eventually leading to the global system in which we now live. The modern world-system came into being when a formerly peripheral and then semiperipheral region (Europe) developed an internal core of capitalist states that were eventually able to dominate the polities of all the other regions of the Earth. This Europe-centered system was the fi rst one in which capitalism became the predominant mode of accumulation, though semiperipheral capitalist city-states had existed since the Bronze Age in the spaces between the tributary empires."
A closer examination of the three components of the world-system reveals the complexity of this analytical framework. Core, periphery, and semiperiphery are, in Wallerstein's apt phrase, "a relational concept." What binds these three units into a system is interaction that generates an ever-changing systemic dynamic. While there is an economic hierarchy of core, periphery, and semiperiphery, the actions of one have an impact upon the others. Moreover, while the defining structural process remains constant, the individual parts of the system change over time.
One reason is the changing nature of the products of significance in the world economy. An example is the indigo industry, which was, for a brief period, an important product in the eighteenth- and nineteenth-century world economy. More broadly, in the sixteenth and seventeenth centuries, agricultural production dominated the economic world-system. By the late eighteenth century manufactured goods were the product of choice, and since the last decades of the twentieth century high technology production characterizes the core nations.
Within this paradigm, world-system analysis stresses dynamic interaction and change. Core nations can become semiperipheral or even peripheral nations. One classic example is Spain, which devolved from a core nation in the sixteenth century to a semiperipheral nation in the eighteenth century.
Conversely, a semiperipheral area can rise, over time, to core status. In the case of Atlantic North America, the colonies developed from external (the pre-Columbian period) to peripheral (the fifteenth to seventeenth centuries). After independence the United States evolved from a semiperipheral nation (the eighteenth to midnineteenth centuries) to a core nation (the mid-nineteenth to mid-twentieth centuries) and recently to hegemonic power (the late twentieth century).
One historical dynamic is the competition of core nations for advantage in the world-system economically, politically, culturally, and often militarily. Wallerstein identifies several struggles between core nations that result in warfare reverberating around the globe. Importantly, peripheral areas and semiperipheral areas are not passive participants in the system. In many cases they strive to rise in status and often rebel, at times successfully, against the power and control of the core nations and the hegemon. This creates policy disputes over strategy and tactics within the core nations. In the late eighteenth century, for example, Spanish diplomacy toward the rebelling British colonies was caught between the desire to weaken the power of England and the fear that the colonial rebellion would set a precedent for Spain's own colonies."