Dependency theory is the theory that explains the outflow of resources from poor and underdeveloped nations to wealthy and developed countries, thereby making the wealthy nations wealthier.
Modernization theory on the other hand is the theory that explains the social change in which underdeveloped and developing countries continue to develop as they adopt modern practices similar to more developed societies.
Also, the Centre-Periphery theory is the theory that defines the structural connection between the developed states (center) and the underdeveloped states (periphery) usually within a country.
