leading dependency theorists include Herb Addo, Walden Bello, Ruy Mauro Marini, Enzo Faletto, Armando Cordova, Ernest Feder, Pablo González Casanova, Keith Griffin, Kunibert Raffer, Paul Israel Singer, and Osvaldo Sunkel. Many of these authors focused their attention on Latin America; dependency theory in the Islamic world was primarily refined by the Egyptian economist Samir Amin. Tausch, based on works of Amin from 1973 to 1997, lists the following main characteristics of periphery capitalism: Regression in both agriculture and small scale industry characterizes the period after the onslaught of foreign domination and colonialism Unequal international specialization of the periphery leads to the concentration of activities in export-oriented agriculture and or mining. Some industrialization of the periphery is possible under the condition of low wages, which, together with rising productivity, determine that unequal exchange sets in (double factorial terms of trade < 1.0; see Raffer, 1987) These structures determine in the long run a rapidly growing tertiary sector with hidden unemployment and the rising importance of rent in the overall social and economic system Chronic current account balance deficits, re-exported profits of foreign investments, and deficient business cycles at the periphery that provide important markets for the centers during world economic upswings Structural imbalances in the political and social relationships, inter alia a strong 'compradore' element and the rising importance of state capitalism and an indebted state class The American sociologist Immanuel Wallerstein refined the Marxist aspect of the theory and expanded on it, to form world-systems theory. World Systems Theory is also known as WST and aligns closely with the idea of the "rich get richer and the poor get poorer". Wallerstein states that the poor and peripheral nations continue to get more poor as the developed core nations use their resources to become richer. Wallerstein developed the World Systems Theory utilizing the Dependence theory along with the ideas of Marx and the Annales School. This theory postulates a third category of countries, the semi-periphery, intermediate between the core and periphery. Wallerstein believed in a tri-modal rather than a bi-modal system because he viewed the world-systems as more complicated than a simplistic classification as either core or periphery nations. To Wallerstein, many nations do not fit into one of these two categories, so he proposed the idea of a semi-periphery as an in between state within his model. In this model, the semi-periphery is industrialized, but with less sophistication of technology