For instance, the value of an agricultural plot of land rises dramatically if it receives a building permit. The key point is that this urban profit is created discretionally depending only on land-use planning criteria. Therefore, this added value should not go into the hands of the private sector but be redistributed and used for the public good. In Catalonia’s urban system, there is a minimum public participation in the uiban profits, established by law'. Green spaces and streets with all its infrastmctures systems needed (sanitation, electricity and water supply) are built and paid by real estate developers. In addition, the public administration will receive a portion of land where it will be able to build up to 10% of the permitted square meters, free of charges.