In the United States, for example, developers are offered a number of incentives to build mixed-income housing, including low-interest financing tools, density bonuses, tax abatement programmes, rehabilitation assistance, fast-tracking of plan reviews and permits, and reduced or waived fees. Emerging and middle-income families living in these units receive an extra subsidy bonus. One of the first projects to be developed through this programme, San Alberto Casas Viejas, has been set in the outskirts of Puente Alto, a municipality with among the highest concentrations of social housing in the Santiago Metropolitan Region.