The concept of dualism employed in this book is used specifically in reference to its structural and territorial dimensions. Structural dualism Indicates the existences on one pole of the farm spectrum of a limited, yet expanding, large farm sector which produces a considerable portion of the total agricultural sales and/or occupies a substantial area of cultivated land. It also implies the existence on the other pole, of a decreasing, but large, small farm sector. Structural dualism is further characterized by a collapsing middle farm sector. The territorial dimension of dualism refers to the contrast between developed and underdeveloped regions within a single national territory.