function more equitably, generating a tax base for housing, educational and employment programs. Policy tools Zoning ordinances The most widely used tool for achieving smart growth is modification of local zoning laws. Zoning laws are applicable to most cities and counties in the United States. Smart growth advocates often seek to modify zoning ordinances to increase the density of development and redevelopment allowed in or near existing towns and neighborhoods and/or restrict new development in outlying or environmentally sensitive areas. Additional density incentives can be offered for development of brownfield and greyfield land or for providing amenities such as parks and open space. Zoning ordinances typically include minimum parking requirements. Reductions in or elimination of parking minimums or imposition of parking maximums can also reduce the amount of parking built with new development increasing land available for parks and other community amenities. Urban growth boundaries Related to zoning ordinances, an urban growth boundary (UGB) is a tool used in some U.S. cities to contain high density development to certain areas. The first urban growth boundary in the United States was established in 1958 in Kentucky. Subsequently, urban growth boundaries were established in Oregon in the 1970s and Florida in the 1980s. Some believe that UGBs contributed to the escalation of housing prices from 2000 to 2006, as they limited the supply of developable land. However, this is not completely substantiated because prices continued to rise even after municipalities expanded their growth boundaries. Transfer of development rights Transfer of development rights (TDR) systems are intended to allow property owners in areas deemed desirable for growth (such as infill and brownfield sites) to purchase the right to build at higher densities from owners of properties in areas deemed undesirable for growth such as environmental lands, farmlands or lands outside of an urban growth boundary. TDR programs have been implemented in over 200 U.S. communities. Provision of social infrastructure Systematic provision of infrastructure such as schools, libraries, sporting facilities and community facilities is an integral component of smart growth communities. This is commonly known as 'social infrastructure' or 'community infrastructure'. In Australia, for example, most new suburban developments are master planned, and key social infrastructure is planned at the outset. Environmental impact assessments One popular approach to assist in smart growth in democratic countries is for lawmakers to require prospective developers to prepare environmental impact assessments of their plans as a condition for