One of the profoundest changes was the transition from collective land tenancy to private ownership and the consequent socioeconomic stratification of the population. While urban expansion in Latin America has spiraled at an unequaled rate, the belief is still widespread that economic development is associated with city rather than with rural life. Many planners are resigned to the fact that migration to the urban centers is an irreversible process, and maintain that it should therefore be guided into constructive developmental channels instead of being allowed to impede national growth. In many cases more damage has been wrought by diverting attention away from depressed rural areas, thereby resulting in a migratory movement swamping urban centers. Agrarian reform, as a process, first manifested itself in Mexico and extended to numerous Latin American countries with varying degrees of efficiency and success. In most Latin American settlement schemes the family farm is the core element, and communities of small landholders constitute the organizational pattern.