However they are beyond the scope of this paper and, as explained in Box 1, they have not been surveyed in the OECD QuASH (2014). This complexity makes the classification of policy programmes difficult, nevertheless a classification is necessary to collect and monitor information. One useful and common classification divides subsidies into supply-side and demand-side. Supply-side subsidies are directed at producers of housing and can consist of direct government grants or subsidies, as well as land and tax concessions for provision of housing or urban renewal.