In the 1970s and 1980s, Soviet archaeologists traced migrations in Eastern Europe to the historical dialectics of modes of production, and, drawing on Marxist theory, conceptualized them from theoretical platforms such as economic primitivism, environmentalism, and imperialism. Because of the close conceptual associations between material culture and society that most archaeologists assumed, migration was more often than not used as an explanatory device. In other words, migration was used to explain cultural and social change. Conventional methods of identifying migration involve the use of archaeological types or material culture styles. Some believe that the migration of the Slavs may be tracked by means of the sunken-floored buildings in which the Slavs typically lived. The obsessive preoccupation with migration as an explanatory device has prevented any consideration of implications, particularly its impact on the emigration area. Emigration typically causes a shortage of human resources, and the abandonment of settlement structures.