by Paul A. Baran in 1957 with the publication of his The Political Economy of Growth. Dependency theory shares many points with earlier, Marxist, theories of imperialism by Rosa Luxemburg and Vladimir Lenin, and has attracted continued interest from Marxists. Some authors identify two main streams in dependency theory: the Latin American Structuralist, typified by the work of Prebisch, Celso Furtado, and Aníbal Pinto at the United Nations Economic Commission for Latin America (ECLAC, or, in Spanish, CEPAL); and the American Marxist, developed by Paul A. Baran, Paul Sweezy, and Andre Gunder Frank. Using the Latin American dependency model, the Guyanese Marxist historian Walter Rodney, in his book How Europe Underdeveloped Africa, described in 1972 an Africa that had been consciously exploited by European imperialists, leading directly to the modern underdevelopment of most of the continent. The theory was popular in the 1960s and 1970s as a criticism of modernization theory, which was falling increasingly out of favor because of continued widespread poverty in much of the world. At that time the assumptions of liberal theories of development were under attack. It was used to explain the causes of overurbanization, a theory that urbanization rates outpaced industrial growth in several developing countries. The Latin American Structuralist and the American Marxist schools had significant differences but, according to economist Matias Vernengo, they agreed on some basic points:[B]oth groups would agree that at the core of the dependency relation between center and periphery lays [lies] the inability of the periphery to develop an autonomous and dynamic process of technological innovation. Technology – the Promethean force unleashed by the Industrial Revolution – is at the center of stage. The Center countries controlled the technology and the systems for generating technology. Foreign capital could not solve the problem, since it only led to limited transmission of technology, but not the process of innovation itself. Baran and others frequently spoke of the international division of labour – skilled workers in the center; unskilled in the periphery – when discussing key features of dependency. Baran placed surplus extraction and capital accumulation at the center of his analysis. Development depends on a population's producing more than it needs for bare subsistence (a surplus). Further, some of that surplus must be used for capital accumulation – the purchase of new means of production – if development is to occur; spending the surplus on things like luxury consumption does