World-systems theory (also known as world-systems analysis or the world-systems perspective)[ 3] is a multidisciplinary approach to world history and social change which emphasizes the world-system (and not nation states) as the primary (but not exclusive) unit of social analysis.[ 3] World-systems theorists argue that their theory explains the rise and fall of states, income inequality, social unrest, and imperialism.
"World-system" refers to the inter-regional and transnational division of labor, which divides the world into core countries, semi-periphery countries, and periphery countries.[ 4] Core countries have higher-skill, capital-intensive industries, and the rest of the world has low-skill, labor-intensive industries and extraction of raw materials.[ 5] This constantly reinforces the dominance of the core countries.[ 5] This structure is unified by the division of labour. It is a world-economy rooted in a capitalist economy.[ 6] For a time, certain countries have become the world hegemon; during the last few centuries, as the world-system has extended geographically and intensified economically, this status has passed from the Netherlands, to the United Kingdom and (most recently) to the United States.[ 5]
Immanuel Wallerstein is the main proponent of world systems theory.[ 7] Components of the world-systems analysis are longue durée by Fernand Braudel, "development of underdevelopment" by Andre Gunder Frank, and the single-society assumption.[ 8] Longue durée is the concept of the gradual change through the day-to-day activities by which social systems are continually reproduced.[ 8] "Development of underdevelopment" describes the economic processes in the periphery as the opposite of the development in the core. Poorer countries are impoverished to enable a few countries to get richer.[ 8] Lastly, the single-society assumption opposes the multiple-society assumption and includes looking at the world as a whole.[ 8]