Immanuel Wallerstein formulated world-system theory which argues that development should be analyzed at the global level rather than just at the national level. The world system is divided into a core (developed nations), periphery (undeveloped nations providing raw materials to the core), and semi-periphery (nations in between). Peripheral and semi-peripheral nations have failed to develop because they continue to depend on the core nations economically and technologically. True development requires ending this external dependence, as nations like Japan and South Korea did through selective openness and state-led industrialization and technology development.