Dependency theory brings out the concept that wealthy nations are becoming rich at the expense of poor nations with the resources from the poor nations flowing to the rich countries. It is a fundamental argument of the dependency theory that poor countries are impecunious and that the rich countries are enriched and through these the poor countries are incorporated to be part of the world system. Dependency theory varies from the way a majority of foreign approaches of studying political growth. Among the major differences is that this approach began in the poor nations. Dependency thinkers from developing countries were largely concerned with bringing out an explanation on the unjust and unfair situations their countries and they themselves had found themselves in. According to them, by nearly any conformist socioeconomic quantifier, poor nations are considered inferior to the first world countries. Third world nations had less wealth, improper hygiene, less education, less military muscle, and were economically and politically subjects of the wealthier first world nations.
In the past, superior countries have taken a large quantity of resources from less superior nations. These resources, for instance metals and minerals are essential in manufacturing jewelry, weapons and automobiles. First world nations would not be as economically strong as they are now without these materials. Wealthy nations enlarged their profits by indulging in slavery.
For example King Leopold II, was the King of Belgium for the period of 1865 to 1909, enforced thousands of poor people to slavery in the Democratic Republic of Congo. This was the period of the invention of the bicycle tire in the early and late 1890s and the subsequent automobile tire. During this period the demand for rubber was high. Rubber vines were prevalent in the Congo, and through slavery Leopold earned millions. The DRC still suffers from the torture and plundering of natural resources during the reign of King Leopold.
Reference:
So, A. Y. (1990). Social change and development: Modernization, dependency, and world-systems theories. Newbury Park, Calif: Sage Publications.