Core countries in the context of "World-systems theory"

The term Third World arose during the Cold War to define countries that remained non-aligned with either NATO or the Warsaw Pact. The United States, Canada, Japan, South Korea, the Southern Cone, Western European countries and other allies represented the "First World", while the Soviet Union, China, Cuba, North Korea, Vietnam, and their allies represented the "Second World". This terminology provided a way of broadly categorizing the nations of the Earth into three groups based on political divisions. Due to the complex history of evolving meanings and contexts, there is no clear or agreed-upon definition of the Third World. Strictly speaking, "Third World" was a political, rather than economic, grouping.

Since most Third World countries were economically poor and non-industrialized, it became a stereotype to refer to developing countries as "third-world." In political discourse, the term Third World was often associated with being underdeveloped. China was labeled "Third World" for several decades in the 20th century before its robust development of the 21st century. Some countries in the Eastern Bloc, such as Cuba, were often regarded as Third World. The Third World was normally seen to include many countries with colonial pasts in Africa, Latin America, Oceania, and Asia. It was also sometimes taken as synonymous with countries in the Non-Aligned Movement. In the dependency theory of thinkers like Raúl Prebisch, Walter Rodney, Theotônio dos Santos, and others, the Third World has also been connected to the world-systemic economic division as "periphery" countries dominated by the countries comprising the economic "core".

Dependency theory is the idea that resources flow from a "periphery" of poor and exploited states to a "core" of wealthy states, enriching the latter at the expense of the former. A central contention of dependency theory is that poor states are impoverished and rich ones enriched by the way poor states are integrated into the "world system". This theory was officially developed in the late 1960s following World War II, as scholars searched for the root issue in the lack of development in Latin America.

The theory arose as a reaction to modernization theory, an earlier theory of development which held that all societies progress through similar stages of development, that today's underdeveloped areas are thus in a similar situation to that of today's developed areas at some time in the past, and that, therefore, the task of helping the underdeveloped areas out of poverty is to accelerate them along this supposed common path of development, by various means such as investment, technology transfers, and closer integration into the world market. Dependency theory rejected this view, arguing that underdeveloped countries are not merely primitive versions of developed countries, but have unique features and structures of their own; and, importantly, are in the situation of being the weaker members in a world market economy.

In world-systems theory, periphery countries are those that are less developed than the semi-periphery and core countries. These countries usually receive a disproportionately small share of global wealth. They have weak state institutions and are dependent on—and, according to some, exploited by—more developed countries. These countries are usually behind because of obstacles such as lack of technology, unstable government, and poor education and health systems. In some instances, the exploitation of periphery countries' agriculture, cheap labor, and natural resources aid core countries in remaining dominant. This is best described by dependency theory, which is one theory on how globalization can affect the world and the countries in it. It is, however, possible for periphery countries to rise out of their status and move into semi-periphery or core status. This can be done by doing things such as industrializing, stabilizing the government and political climate, etc.

In world-systems theory, semi-periphery countries are the industrializing, mostly capitalist countries that are positioned between the periphery and the core countries. Semi-periphery countries have organizational characteristics of both core countries and periphery countries and are often geographically located between core and peripheral regions as well as between two or more competing core regions.

Semi-periphery regions play a major role in mediating economic, political, and social activities that link core and peripheral areas. These regions allow for the possibility of innovative technology, reforms in social and organizational structure, and dominance over peripheral nations. These changes can lead to a semi-periphery country being promoted to a core nation. Semi-periphery is, however, more than a description, as it also serves as a position within the world hierarchy in which social and economic change can be interpreted.

Unequal exchange is used primarily in Marxist economics, but also in ecological economics (more specifically also as ecologically unequal exchange), to describe the systemic hidden transfer of labor and ecological value from poor countries in the imperial periphery (mainly in the Global South) to rich countries and monopolistic corporations in the imperial core (mainly in the Global North) due to structural inequalities in the global economy.

Due to biased terms of trade and the undervaluation of labor and goods from the global South compared to the North, poor countries are forced to export a much larger quantity of labor and resources than they import to maintain a monetary balance of trade. This enables the global North to achieve a net appropriation through trade, fostering development in the former while impoverishing the global South.