Preferential property tax treatment is an instrument of land use policy that is used to promote preservation of existing preferred land uses. A reduction in the tax burden is provided to property owners to encourage and enable them to retain their land in its existing use. All states provide property tax relief for agricultural land. (The District of Columbia does not have a program for agricultural land.) Other land uses that widely receive preferential treatment are forest land, recreational land, and open space. The most common method of reducing the tax burden is to assess the property based on its current use even though this may be less than its market value.  Other methods include a reduction of the assessment ratio for qualifying properties, tax credits, and exemption in whole or in part from the property tax. In exchange, the property owner in many states has to maintain the current use for a specified number of years.