When the World Bank recognized that re-settling populations also created, they defined a new relocation policy according to which the social impact of hydroelectric projects in Aguamilpa and Zimapán (Mexico) would he evaluated. Gallart and Greaves describe this process in detail and underline the difficulties facing this type of work. Lack or hiding of information, lack of decision making power, lack of communication between executor and monitor, coordination before, during and after the physical relocation of the population, etc.