Several case studies based on real-world situations in rural development can serve to illustrate specific points. In some Latin American countries there has been sufficient continuity of settlement history to produce an evolution of spatial concepts. In Venezuela, the policy of "plowing the oil back into the land" has generated similar rural development and settlement projects. The initial experience in Venezuela proved that agglomeration is an essential prerequisite for the introduction of amenities and the organization of production. The Dominican Republic has been notable among Latin American countries for its attempts to colonize new lands, due in part to the need to bolster its sparsely populated frontier against infiltration, and the need to integrate its rural population. The experience in the ejidal movement and other rural settlement in Mexico indicates that economic and social efficiency are interdependent and must be dealt with in an integrated manner.